Rather than a dancer, I would think that a xi style ninja (I know, I KNOW, ninja supposed to be enfeeb dps, and ninja kinda broke 11, just wait) could be an interesting evasion tank. I really enjoyed the play of balancing shadow casts, it required a lot of up-keep and timing, it was a bit skill intensive (more than current pld is). So lets not call it ninja, or dancer, lets call it "Ative Casting Dodge Character."

At present, both tanks have the same ehp. I would see no reason not to continue this trend for all future tanks. Not that odd for a martial/eastern class--monks and blackbelts have always had ALL the hp. From a balance perspective, as a pld, I would resent a new tank with a higher base line eHP. Now, (in theory) warrior gets a healing bonus, paladin gets a flat damage mitigation bonus, so we would need to add some new flavor here. This would be the passive bonus that is the buffer to keep the tank alive should thier activie mitigation fail--basicly "should rng decide they need to die" and they fail to dodge. Would be silly to make it just "always dodge x % of an attack" cus that's just nimble pld. Perhaps a deathward style move (like sentinel/snow in 13, not that I have much positive to say about him) that prevents any attack which hits the ACDC for say, 30% or more of its total health from killing it (leaving them with 1 hp, next attack would kill of course since the ACD now has less than 30% hp to loose).

The class would also perhaps lack flat mitigation cool downs, getting only cool downs centered around its dodging. Maybe, the main enmity combo grants 1 shadow at the end, they ahve two - three spells on lenghty (15-30-45) cool downs that are timed to cycle complexly together, a major cool down just resets all shadow cds (or one that acts as an instant cast). Perhaps their three minute coold own could be two instnat shadows (I feel all tanks should have one button that says "this next attack, this one next attack, I can solve this." For PLD this is sentinel, for War this is thrill of battle.

I don't think it should be possible for a tank to keep 100% evasion, but 60-75% with "perfect" play could be reasonable. The tank would be cured at the rate of their total hp as a pld, but take the damage of a warrior when hit. Thier play would center around choosing exactlyw hich attacks to mitigate / what time periods to be evading. This tank would be essentially invuln for some periods, but need heavy healing for others. They would be the hardest class to heal while taking damage, but be able to give their healers rest periods.