I think some debloating is in order, but less in regards to "total power level" (that has to be done via encounter design, seriously) but more in well, raw bloat.

For sake of individually feeling powerful, tanks should probably one "rotational" defensive tool (something like a Paladin's frequent self-healing on abilities or Gunbreaker shielding themselves), one short-CD and one long-CD. No more 3 long CDs, instead of one really powerful one. Rampart is what we start with as a role action, each tank gets a trait to upgrade it into something better, and make them diverge more wildly. Short CDs could also be more more distinct, with different CD and effects (TBN already is a bit different from the other 3, but there's more room to play with there).

This in turn would then allow to tune encounters better: If we can't CD 4+ things in a row easily, and have this variability between stacking CDs vs chaining them, encounter damage can be tuned more precisely.

If I had a wish-list for re-implementing things, I'd do:

* Paladin: Support tank. Various ways to help others, which in turn lowers own CDs. Longest CDs by default, shortest or second-shortest in a group. Passively regenerates 10% of all damage taken back over the next 6 seconds. Support baked into the core kit, like spending instant spell + mana on Clemency should be preferred whenever someone else has damage over nuking with it, taking damage for someone else increases own damage output, that kind of stuff.
* Warrior: Sponge tank. Dealing damage passively stacks shields on self. Damage taken passively decreases the lower health is, in return for lower base damage reduction than other tanks. More HP, but from full health suffers more damage than others. CDs regenerate health and increase max-health further, but only decrease damage by quite little.
* Gunbreaker: Technical tank. All abilities have 25y range and a second animation if used that way. Various abilities move backwards by 5-10y, allow a single ranged attack, but for one GCD the enemy won't follow yet (this would be basically Continuation v2.0). Cartridges built in melee, expended while at range, granting non-stacking shields. CDs focus on automatic effects.
* Dark Knight: Drain tank. Direct damage reduced significantly, however most attacks apply stacking DoTs and all DoT damage heals the Dark Knight. Invuln fires automatically, no player input needed or even possible. Shortest CDs otherwise, but skills need to be timed well to be effective compared to the other tanks.

Anyhow the underlying point would be: less buttons, in return more meaningful differences. Some can be offloaded into passive things which is still good so long as the effects are significant enough to be constantly noticable!