I'm not sure what those bars signify
the bars signify the defensive power of the armor to what damage... the reason it is bars and not numbers is because depending on the depth the equipment in question may have its stats heavily reduced

Armors like wolver line should be nerfed so that it gives less armor or the other "tanky" armors buffed
cobalt armor has more defense than wolver

im hearing "tank tank tank" an awful lot here... theres no holy trinity here, its not your armor IT'S SKILL

Actually, I think over half the monsters in the game deal at least partly normal damage, even on tier 3. Trojans, gremlin thwackers, blast cubes, retrodes' melee attacks, and probably more I'm forgetting do pure normal, but zombies, devilites, mecha knights, lumbers, and others all do partially normal damage. There's almost nowhere in the game where normal defense doesn't help you.

I suspect the OP meant the amount of normal defense isn't substantial, but I don't think he realizes that some armors give more defense than fits in the bar display, making it difficult to compare them. (Even if we knew precisely how much difference each segment of the bar makes, which we don't.) If you try equipping one piece of Volcanic Plate, I think you'll find your average defense bar (helmet icon at bottom of character window) for normal is more than half full.

In any case, "tank" is not a role in Spiral Knights, any more then "healer" is. Nor should they be. Spiral Knights is an action game where one of the major important skills is not getting hit. Not to mention that getting hit does not generally "save" anyone else from being hit, so even if you could somehow take the damage, it's not actually helping the party.

The roles in SK are swordsman, gunslinger, and bombardier. And frankly, those roles have too MUCH reinforcement, if anything, which is why the armors that buff specific weapons are far more popular than others. I don't think they should have ever have put weapon bonuses on armor in the first place, but we're probably stuck with them forever now.

There are some armors that give more health than others, but giving increased defense is frankly better than giving increased health, because if you get increased health you also need more healing to repair the damage you take. Perhaps the super-defensive armors that give you speed penalties should give you more types of defense, but I'd wager they'd still be quite unpopular.

I am with khamsin, armors with sheild bonuses would be excelent, sheild rechage, sheild health, and recharge delay would be the easiest, but ones that add to sheild resitances/defences would be nice as well.

Man you just really like tanks, don't you? They don't automatically make for "more coop", you know; that is pure nonsense. Did you ever play the excellent Zelda: Four Swords Adventures? You may have noticed the absence of a tank in that; it's one of the best co-operative action RPGs I've ever played (not that it's a terribly long field) and certainly one that SK appears to be heavily modeled on. I actually started playing SK because it was described to me as basically Four Swords with Ian McConville art.

Tanks are rather incompatible with SK's combat mechanics, which are heavily reliant on evasion rather than damage absorption. The range of damage types doled out by monsters on different strata is incompatible with the idea of one guy who takes a bunch of punishment whilst their teammates pick off monsters - sure, all creatures do an amount of Normal damage, but it's secondary. A strong Piercing attack, say from an Alpha Wolver, will ruin a guy in pure-Normal armour. You can obviously mix and match different armour pieces to defend against different attack types, but it often leads to a bit of a crap loadout that's not much good against anything in particular - which is not what you want from a tank.

Tanks as a squad pivot are also incompatible with SK's party mechanic. Reliance on a tank immediately messes up random drop-in parties by encouraging squad-building, gathering a team before taking on the Clockworks, rather than just jumping in and having a great ol' time anyway. Of course, you currently can assemble a squad before setting off, and even tailor your loadouts to complement each other - but it's not necessary to the degree that reliance on a tank could very easily make it.

It's not a viable or necessary role, as Antistone quite rightly pointed out. It doesn't magically improve co-operative play, and would require such drastic rebalancing that what you'd end up with would be a very different game to the one that thousands of people currently enjoy.

You're right, I haven't run any Shadow Lairs, but I think it's fair to say that neither have the vast majority of players; an overwhelming proportion of the game is played by people in drop-in parties. The points about the combat mechanics stand; SK's combat is far and away about evasion over absorption. Did I come across as freaking out? I'm just trying to explain why I disagree with the OP's assertion.

I don't think tanks would break the game. I'm pretty sure the game would break tanks, though.

The idea of having a "class" focused around blocking/living longer is interesting, but they'd need more of a draw than just that; Else all they're good for is making your typical runs go slower. As in, except for Shadow Lairs, you're typically going to want everyone geared out for DPS. A "shield bearer" won't be able to pull their weight in your average run.

I'm drawing blanks on how you could properly implement them into SK's current system. [Without the introduction of buffs and such.]

SK is plenty co-op, if anything the addition of a "tank" class would make it LESS! If you have ever played other MMOs the tank class is the one people pick when they want to solo stuff. With the correct choices on skills, equipment, and other things you can walk through areas like the touch of death and lay waste to anything that crosses your path while not having to worry about your health too much. The only possible way you could add a "tank" class to the game would be if you gave it a rather large damage reduction to balance out its greatly increased survivability. And people are more then willing to give up defense for extra offensive output.

Armor: You specifically mentioned the Wolver line, as everybody does. Cobalt/Jelly has more defense then Skolver, Skelly has more defense then Snarby, and Grey Feather has more defense then Vog. The special damage anyways, Normal damage the Wolver lines beat them by a little. You'll notice that even with armors with better defense the Wolver lines still get used a lot, because people want the bonuses more than the added defense.

Health: There are a few pieces that give higher health then others, one of them is Ancient Plate set. I think you're missing the point of the plate lines though. They give insanely high normal defense while giving a decent special defense (a shadow plate line would be nice though). "Health should be rebalanced so that health is not on par with tankier people. This way, there is more reliance on a tank, hence more Co-op." A class specifically designed to take a beating goes against the entire idea of SK. You are supposed to shield and dodge, much like old school Legend of Zelda. A tank also classically needs a healer to keep them alive. Tank holds aggro (and has their face pounded), healer keeps the tank on their feet. You can't add a healer class to SK without completely breaking the game. And yes, I know we have healing items and hearts, they're a limited supply, a healer has an infinite supply.

Shields: Shield that gives more defense but make you move slower/ASI debuff? Nobody would use it. People are willing to sacrifice defense for extra ASI and damage, to the point that they're willing to wear Vog into areas it has no business being to keep their ASI. You can find swordies in T3 (often laying on the floor) with a Swiftstrike because they want the added ASI, and that shield breaks from a single attack from anything in T3.

Gunner: ALL FOR IT!!! Show the Gunners some love for once!

~Gwen