I think progression could be improved upon

People tend to go towards one set when the game is about branching out.
This is the trend of chaos and black kat, wolver armor, etc. versus specialized armor, as well as the desire to craft as few weapons as possible. They do it because the game gives them the incentive to do it in spite of itself- it's cheaper to craft chaos/seerus/black kat than it is to plan around random scenarios. Since much of the fun to be had is in replaying levels with new gear, it would make sense to force players to branch out.
Buff Every Piece Of Armor (that isn't black kat/chaos/seerus)
I suggest going across the board. Start anywhere. Come up with a nice buff. Implement it. They should all be about as strong as chaos, but in different ways.
Doing this will provide further incentive for players to craft armor. They wouldn't have to get chaos/seerus or get the wrong end of the stick. Most of the armors can be fixed via stat gains/losses, but a few more stats would really help out here. This can all be done later, but the process of fixing up old/bad armor, say, once a month, would be the real change that's needed.
Raise the drop rate of orbs and fire crystals... but also the need for them.
Currently the knight only needs one set of armor and a single weapon to progress past the hall of heroes. This is likely intended as a minimum amount of gear, but it is often treated as the maximum amount one should craft. Hence, we triple the requirements. 3 sets of armor, 3 shields, 3 weapons. Then, we double the drop rate of orbs and fire crystals. That way, newer knights get to the Hall of Heroes, grind about the same amount, and come prepared into the new tier. This should carry over to radiant fire crystals, such that they are able to heat three times the gear with twice the fire crystals.
Make status effects harder on the knight when not resisted, and easier when resisted
The knight has about 5 degrees of resistance. Here is what I'd like to see happen-
Negative Resistance = should mean the knight is on death's door immediately. Think curse length status effect.
No Resistance = should mean the knight is heavily harmed but not quite dead.
Some Resistance = harmed greatly, almost as if no resistance as this is chaos cloak + seerus
Normal Resistance = i.e. 2x vog for fire; +8; the knight should be barely touched
All In Resistance = 2x vog + trinkets + UVs etc.; the knight should be immune
The actual values players use for these are-
Negative anything
0
3
9
12+
Where one point is a low. All this takes is tweaking some numbers, and would make the game much more dangerous for glass cannon users.

A complete armor rebalance is long overdue, and while it would be hard to figure out, it would be very worthwhile in the long term.
I would say we can introduce some new "gear boosts" to the game to influence playstyles. Here is an example of things we can use as buffs based on things that are already in the game:
- Bomb Fuse Time Reduction
- Bomb Radius Increase
- Gun Projectile Lifetime Increase
- Sword Charge Time Reduction
- Sword Range Increase
- Sword/Gun/Bomb Movement Speed Increase
- Sword/Gun Bomb/All Charging Movement Speed Increase
- Shield Recharge Speed
- Shield Bash Damage
- Shield Bash Distance
- Dash Cooldown Speed
- Dash Invulnerability Time
- Dash Distance
- Status Infliction Chance Reduction
With just these changes it can completely overhaul how you interact with weapons. If all wolver sets had a +2 to swords combined with a +1 in another regard at 5*, it would make them much more unique. Imagine if Vog Cub had sword attack speed + 2 and sword movement speed + 1. This allows you to run in and hit your enemies quickly before ducking out. Meanwhile, skolver could have sword damage + 2 and sword range increase of +1. This means they can hit enemies slightly further away than others with their swords, but they hit harder. Snarbolax could have sword damage +2 and a sword charge time reduction of +1, meaning they are more based around unleashing powerful sword charge attacks. Starlight could have sword movement speed increase of +2 and sword charge time reduction of +1, making them all about getting in close to enemies, unleashing a powerful charge attack, and then getting out of there.
Under this system, you can balance each line of a set to be more unique instead of simply being a choice between status resistances or damage resistances. You can also use some nerfs for certain weapons, such as chaos receiving a bomb fuse time increase to make them less useful for bombers who want everything around them dead as fast as possible.
I will say the other tidbits of the suggestion do look nice, but I would definitely want a testing server to try them out first. Crafting a variety of gear is encouraged by the game for longevity, but not through its story. I think having rank missions grant players enough orbs to craft 2 complete sets at every tier would be a good way to encourage crafting more items so long as the three full sets are required to pass the hall of heroes.
The only downside to giving the players more is that people may not know where to start, and while the hall of heroes does help with this, it's not always the most helpful. I would recommend missions giving the player "recipe tickets" that they can exchange at the hall of heroes at any tier with the person who's ticket is granted. IE, you may get an "Echo Hall of Heroes Ticket", which you can use to exchange for any of Echo's recipes. This should help with the burden of recipe costs when requiring more sets to pass the hall of heroes.
Lastly, plus one to the status idea. Statuses are currently still way too punishing even if you resist them. Even if complete immunity is impossible, being able to shrug off a status shouldn't be impossible - perhaps high resistance gives players an "alert" type effect to the status so they cannot be repeatedly inflicted with it?

to Fehzor simple and seems time efficient to implement
to Fangel so you want to make game even easier + more confusing?
In the end there will be just a couple of pwnage sets again + your idea do require a lot of balancing, which is waste of time.
We use Chaos and Kat sets because it is damn easy to dodge attacks in that game (excluding bad level designs such as shadow lair or c42).
But instead of all of this I would be happy if developers added some new move sets to existing monsters (I'm not asking for better AI because I guess it is too hard to develop)
~
your dark souls git gud fan
I really like those ideas. Though, we have came so far with our current system and metas that i dont think its a good idea to change everything like that, at this point of the game's lifetime.