The thing is, using Chaos doesn't make you a Glass Cannon because
a) On Elite in S6, everything kills you in a few hits either way
b) Chaos provides defence almost as good as other sets, as well as a fully fledged health bonus

i want to get CIV, although it probably wont happen for a while

I see some of this stuff here and there actually.

Armor:

1. Nameless gives elemental defense and VH ASI on guns. I was even considering making this just for the ASI in lockdown. Being one of the standard gunslinger line sets, it's naturally one of the sets a gunslinger goes for to cover all damage types. I see this.

2. Mercurial is good for lockdown for shock resist (and if you get some piercing defense UVs, it'll do good against FF/BTB; also possible to achieve shock immunity with ease). I see this.

3. Grey Feather is probably the best defense set for SL IMF. Admittingly, I don't see this cause SL IMF is unpopular.

Shields:

I'll give you this; I don't see much of any of those shields.

Swords:

1. Leviathan is still good. Though outdamaged by Acheron, it's pretty balanced and useful vs all enemies with steady damage from normal and charge attacks. I see and use this.

2. Glacius is a 5* brandish, thus it's naturally great. Freeze is a powerful status when you know how to use it and if it fits your playstyle. I see this.

Guns:

1. Alchemers? What gunner do you see without these in PvE? Plenty use them in PvP too. I see and use them...

2. Valiance is decent. Mediocre in PvE, but it's definitely a staple in PvP loadouts. I see and use this.

3. Sentenza is decent. Easier to grab than Carbine and is good in PvP, mediocre in PvE . I see this.

4. Callahan is decent. Valiance is better than this vs Fiends and Wolvers, but still has stun and a decent charge attack for sniping in PvP. I see this.

5. Biohazard is decent. Works great in PvP, but underwhelming in PvE. I see and use this.

Bombs:

Bombers are a dying breed, but I still see all mist bombs, except Stagger Storm, being used by hybrids.

I'm a bomber-gear focused knight, and yes, the lack of radiants will kill us off. Smaller bomb radiuses from 4* bombs make it more dangerous, and 5* ones require more CTR from armor/trinkets, and damage bombs have less damage at 5* heat level o than 4* heat level 10.

@OP: You have a point, but part of it is how OOO has (un)balanced weapons and armor. Maxing out damage, ASI, and CTR on weapons benefits people a lot more than defense-themed armors. Also, some of that stuff is very situational, e.g., Heavenly Iron is SL gear and has massive shock penalty, even if it does have good bonuses. Azure and Aegis? Pretty much useless, it has no status resistances or weapon bonuses, and protects against the easiest types of enemies.

Deadly Virulisk: Specific for slimes, not that hard of enemies and easily can get the damage from other sources, like Skolver (even if it is just for swords), and there will typically be other types of enemies also in levels.

Volc Salamander: Even worse, it defends against different type of enemies than it has bonuses versus.

Bombastic: Most bombers go for CTR first, and for fire defense for FSC. Any bomb can do ok with decent CTR, and mist bombs don't need damage increases.

Mad Bomber: A thing of the past before Chaos was buffed to be the same thing (barring additional curse penalty) except that it affects any other gear you decide to take along with bombs.

And so on... most of the unused gear does not provide either the DPS or sufficient other use (safety, statuses, etc) to be as useful as the "popular" gear.

Time for a ton of opinions that I know are probably wrong, but they're just my views. /shrug

Valkyrie has negative fire resistance. There's not much more to say, being burned to death is never fun.

Ironmight, due to the way defense works, can be compared to Azure Guardian in that they both defend against the easiest type of enemy, and while Ironmight has the Stun defence over Azure, it also decreases your Attack Speed.

Volcanic Plate Set could arguably be good, but again, ASD kills it much like Ironmight. The shield, however, is actually pretty good.

Omega Shell, while more or less being the most balanced shield in the game (not balanced in terms of the risk:reward ratio is good, but balanced in that it can be used anywhere). It can take a couple hits from pretty much everything, but all that shield health only goes so far when the only defence it has is against Normal. A specialised shield would be better-suited, however if you only wanted to get one 5* shield and only one, Omega Shell would be a good choice.

Leviathan Blade is good, just unappreciated. Not much to say here.

Fearless Rigadon and Furious Flamberge are rarely used, for good reason. The Stun/Fire chance is way too low to possibly make up for the damage loss over FF/BTB. Also, like FF, they have a... pretty useless charge, to say the least. This is where BTB outclasses all three (although you can't rage-craft BTB to death like you can a Flourish).

Triglav and Suda are good, but due to the choices people make in armour, Sealed Sword lines benefit more from Dmg Boosts or ASI. Or even CTR, in terms of DA. If they were only faster...

Glacius is rare because everyone basically falls over in love and praise for fire damage, or they see that Voltedge requires PvP and they immediately assume it's better (and IMO, it is).

Cold Iron Vanquisher sucks. That's about as blunt as I can be. Like I said earlier, "This is literally like getting a Cautery Sword instead of Tempered Calibur. It's completely outclassed, and you shouldn't do it."

Saying Alchemers are rare is like saying Chaos is rare. Not even going to start on this.

Valiance is generally put off because of the fact it has pure Normal damage, and is relatively weak when compared to other choices. (I quite honestly only made my Valiance for PvP, but now it's my staple PvE gun because I never realised how good it was until I actually made it.)

Volcanic Pepperbox is rare for a bunch of reasons. It'll take soooo very long to describe why. Well, here it is: we have Blitz Needle.

Callahan and Iron Slug are exceptionally weak, the latter being one of the weakest 5* guns in the game if not the weakest.

No one makes Neutralizer or Biohazard because of two main reasons:
1. They spend their Bark Modules on a Pulsar and don't bother farming for more tokens to get the Catalyzer.
2. They DO get the Catalyzer, try it out, and put it aside, thinking it's useless because of its slow bullets and/or relatively weak charge (they're, of course, forgetting it's only a 2* weapon).

Supernova... I don't even want to start on this. Polaris is better. There's not much more to it. Polaris has shock, and is specialised against one of the most farmed areas in the game. Let's not forget that Beasts and Gremlins, the thing Polaris is least useful towards, either dodge the bullets or are better off being fought with a sword, or even a bomb for that matter. Now, taking a look at what the Pulsar guns shine in:
Flinch-locking Gun Puppies, Polyps, and Howlitzers when you can't reach them with a sword. And guess what, Shock only makes things that much easier. Plus, Gun Puppies/Howlitzers are weak to Elemental (obviously), and the final turret is neutral to it.
Now, one argument for Supernova that I hear from a ton of newer people who just got their Pulsars is: "I want to make Supernova because it will always knockback. Shock sometimes stops the knockback." While this is true, the shock on Polaris also keeps enemies in place, when they're not getting pushed back, so either way enemies aren't going to advance unless they do something right at that teensy tiny moment after a spasm and before the next shot hits.

Moving along...

Plague Needle does 105 more damage against Piercing Weak enemies than Blitz Needle does to Neutral enemies. I'm going to use my Volcanic Pepperbox argument here as to why it's so rare: "we have Blitz Needle."

Haze Bombs other than Shivermist, huh? Well, let's look at it this way. We have Shivermist, a staple bomb. Dark Briar Barrage, which takes care of anything a Haze Bomb could take care of, and Dark Retribution, which takes care of anything Dark Briar Barrage couldn't take care of. So that leaves... Constucts? Well, if I can remember correctly, Constructs are the easiest to fight when they're frozen in place. What Mist Bomb does that again? Oh yeah, Shivermist Buster. Ice Stratums? Dark Retribution works just fine too.

On to the few armour sets I missed:

Grey Feather Set is, in my opinion, one of the best armour sets in the game. I quite honestly have no idea why it's so rare. Oh wait, yes I do. Because when people have their 4* Miracle Set, guess what they're about to make? Chaos. Why? Because a large percentage of peoples' first few 5* sets has some sort of Fire Resistance, so they have no reason to make another armour set that just has more fire res (let's face it, there are a ton of fire resistant sets).

Mercurial Set is rarely made because Skolver and Mercurial Demo exist (the latter being better in every way you could think of, it still has max shock res, it still has MSI, it has an added Bomb Damage Bonus Low per piece, and of course, elemental res is a lot more useful than Piercing res).

And last but not least: Dread Skelly. Again, I don't know why people would put this off so much. Probably because most people think that the Poison + Freeze res is more or less useless to suit their needs, so they end up making a different shadow armour, or not having one at all. And of course we have Snarbolax, which fills the role of Dread Skelly, except with a Sword damage bonus. While it's true that Snarbolax doesn't give as much Poison and Freeze resistance, most people just brush that aside.

And thus ends my badly made opinions.

The logical order of progressing through the game involves making a "good" set of items that you can take anywhere and kill anything with. These "rare beauties" are not seen by most players as being on par with many of the items that you mentioned, and for good reason: A large portion of the items in Spiral Knights will lead you into believing that they do something, and then shoot your knight in the foot when it comes time to use them.

The following is a list of the items you mentioned that I don't have yet:

Azure set 0/2
Nameless set 1/2
Deadly Virulisk set 1/2
Volcanic Salamander set 0/2
Bombastic Demo set 1/2
Mad Bomber set 1/2
Ironmight set 1/2
Dread Skelly set 1/2

I started on several of these, but I will probably never finish any of them unless I am allowed to do so in a timely manner.... that is, if the radiant drought is lifted. Offensive armor was better than defensive armor to boot for the reasons that Zeddy summarized quite well, and now that armor is tedious and expensive to heat, defensive armor has no place in Spiral Knights whatsoever. Besides- why get it now, when OOO will just turn around and release it but better? Thats what happened with the kat hats and dread skelly.

So it is with things like venom veilor- a bomb that benefits largely from being heated... but is seen as being lesser than the shivermist buster. People will still use it and craft it all right, but without the resources to pump into it, it'll remain a level 1 item at the back of their inventory until they feel like goofing off with it again.

Gee, this is sure a head scratcher! Why would I choose DS with it's wonderful extra +1 poison and freeze resist and teensy extra shadow defense over Snarby's amazing VH Sword DMG?

Come on, Tweeter, this isn't hard to grasp...Dread Skelly isn't even a sidegrade, it's just a placeholder for something better, that being Snarbolax. Freeze resist doesn't help much at all where you would usually be frozen (Silversap and Freeze Vents) and poison isn't that lethal of a status to build resistance against. Defense is already laughable because of how it works in this game, that teensy extra amount of shadow wouldn't protect you any more than Snarby.

So, from what I understand, you'd give up 28% extra damage just to get +1 freeze and poison resist? That's silly to do, especially considering that you have both of them. But seriously, suit yourself, no one is stopping you from making whatever you want, but don't question why people are choosing to become stronger and more formidable. You alone are holding yourself back, for whatever reason I do not know.

And by the way, defense is fundamentally not as great as offense in most games; it's only good if you're a player that gets hurt many times.

From a Vog (Let's say this is defensive set for the sake of argument) -> Chaos user, I'll tell you what happens to a lot of players.

You start off inexperienced, in say FSC; at this point in time, you'd value your fire resistance so you don't get hurt as much and are able to simply clear it easy with a cushion of resist. Then something clicks after playing it 20+ times; all of a sudden you can clear the rooms in 25 using muscle memory, you can dodge Vana as if you could read the guy's mind. You're not roasting from the fire status. What's happening? You're getting good at the game! Know what's happening at this point? Your defense stops being useful. Why? You're not getting hit, and as we all know defense only applies when you get hit and only when you get hit.

So what happens now? You don't need the defense because you're so good. Suddenly you want to clear the place faster. Now you want to feel more powerful. You want to get offense. You then put away your defensive set with heavy fire resistance. What do you need it for? It's not like you catch fire anymore. You equip your Chaos set and let your attacks loose. Suddenly you're hitting harder and enemies are trembling at your feet. You're clearing the place in record time.

...you feel spectacular. Don't you see? As long as you're good at the game, you don't need defense. Defense relies on error to be useful. Offense relies on skill to be useful. People want to naturally better themselves as players, not stay a damage sponge.

And Sentenza, it's outclassed now cause Carbine does the same job, but with poison. However, Sentenza is still used because people are able to get it without the need of the event; it has the benefit of being easily obtainable.

How many times has someone died to poison unless it's in C42 where fire is absolutely all over the place? You need to be close to dead or on fire for it to be considered a deadly status.

Lockdown, maybe, cause people underestimate it and charge at you with very weak attacks. But in PvE, it isn't horrible at all, just annoying cause your attacks are weakened.

Poison is only bad if you can't dodge well or if you're constantly overwhelmed.

Your damage is reduced by 50% by poison, I say as long as you have a decent amount of DMG bonuses, it isn't that horrible of a debuff. If you aren't running around waiting for the debuff to go away, you're making a big mistake; poison doesn't prohibit movement so there isn't much reason why you wouldn't be doing that. If you're continuously hit while poisoned, that just means you need to practice dodging, kiting, and cool off on attacking before heading back into the fray.

I wear Chaos constantly, I'd be lying if I said I didn't kite non-stop.

14 seconds of poison is harsh, and a 50% decrease in damage is huge.

@Dibsville
You seem to be using a slippery slope argument, you should be careful with that when illustrating your opinion.

I agree with Shadowstarkirby, poison isn't as bad as other statuses

Also, Many of these "beauties" aren't as good compared to other equivalent equipments.

^Subject line needs no explanation and are you forgetting the cutter line?

I see valiance, calling BS on that one up front.
Forgot bombs in general. Also the Dragon Scale set and Silvermail. You could have only listed the over used ones, it'd be simpler to say "Why are these the only things used? Also, shiver is pretty much for FSC when it's used.

I am kind of amazed that people don't give it a freaking rest about how everyone clearly goes for
the Vog damned most powerful gear.

@Blazzberry Well excuse me Mr-I-have-every-dang-thing

I use Sudaruska and Triglav in my main loadout.

Valkyrie:
Valkyrie was my first 5* set, because I wanted to go around spamming GF charge (...and then I upgraded my Faust to 5* and realized its charge time wasn't worth it). Eventually got around to doing Vanaduke runs in Valkyrie set lol.

I still use it now for fiend stages, mixing and matching offense trinkets and pet skills to get max damage guns, swords, and gun ASI while having relevant defense.

Heavenly Iron set:
I eventually made this because I was tired of people being creeps to me when I used Valkyrie, but soon after I made this sword set, I picked up guns, so it's been unused.

Sudaruska/Triglav:
Khorovod (the then-highest-level Troika) was my first love. My first sword craft was Troika, and I took it straight to highest level before I ever crafted any higher level armors. For compounds, I like to bring a vortex+triglav combo. For a few weeks, I was into doing Troika-line Vanaduke fights (use the charge to attack through the inner layer of fireballs), water to open up room to attack. For a while, they had nerfed the charge attack, removing AOE rocks that did extra damage and replaced it with a weaker single-hit charge. Eventually, they made the charge a double hit, which I approve. Actually, the Suda/Triglav charge as it is right now is weaker DPS than the Khorovod charge that I liked, but it's far more consistent in its mechanic, so it's good enough :)

Neutralizer/Biohazard:
Neutralizer combined with Electron Vortex is my team combination of choice for 4+ monsters in FSC. I can hurt more monsters at once with Neutralizer+vortex than spamming Nova Driver normal or charge attacks.
When I finally got around to soloing Grinchlin Assault with minimal deaths (0-2), my most successful loadouts used Biohazard as the main gun. The slow bullet kept gremlins dodging instead of running towards me. Of course, I used double-switch techniques to use unlimited Biohazard spam, but it was still my preferred weapon for the run.
For both, I only really use the charge when trying to time an interruption (ex: rocket pups) or when combined with Vortex.

Callahan/Iron Slug:
I only use these solo or duo PVE. If I'm with a party, it just slows kills down to take too many hits. In PVP, well, I don't like how you can't turn while shooting, so it's very incompatible with my playstyle. I wanted to believe in Iron Slug. I wanted to prove it had its use if I could perfectly double-switch. But no, aside from the things that Callahan is ineffective against, Iron Slug does exactly the same damage as neutral-damage Callahan with no status. After a certain depth, you need to shoot twice to interrupt enemies, so the whole gain of sacrificing DPS for safety gets diminished. -_-;

Alchemers:
Nova and Umbra are my main guns of choice in PVE. If anything, I avoid the status alchemers in PVE. I'm surprised you listed these as under-rated. Even playing the legit way, their charge attacks can demolish (OHKO) monsters in groups of two.

Valiance:
In PVE, also only use it when solo/duo, because it's very much a single-enemy weapon. In PVP, I also only see it as a dueling weapon. For especially-good opponents, I need to stick with Valiance than Alchemers. Also, it's pretty great combined with Recon's deathmark in PVP.

Nameless:
If I didn't make Justifier already (same bonuses), I would have made the Nameless set. Man, in Lockdown, it'd be goodbye to shivermist bombers, haha. If the gunner update doesn't impress me, I'll make it.

----------

I've always preferred to be a glass cannon. When I started out, I was given a wolver set, but I crafted Troika and took it to 4* as soon as I could. The only reason I ended up leveling up armor was to get into T3, then to get better curse resist for my (then) Faust. I also insisted on doing FSC runs in Valkyrie (in the days that people made Vog and Skolver was a rarity) and got kicked out of runs because of it. I wanted to be a cool hybrid (got my Fallen set for all-weapon ASI) so I made Chaos Set (you know, with its total bonus of Attack:Med on all weapons)... and then it got buffed to be a total of Attack:VH, Ctr:VH and it became the perfect set for me.

If I wanted to care about defense [PVE], I would look at the shield's resistance. If you use armor for defense, that means you're getting hit. If you shield, you don't take damage. If you're defensively-minded, you'd obviously aim for taking 0 damage over taking any damage >_>;
I have a dragonscale shield that I use(d) when feeling rusty for FSC, but again, I prefer to kill quickly and don't care to roll for UVs anymore, so SSB gets my vote most of the time.