As it has been said 1000x over evasion tanks are always going to be broken. Either
A) their eva is so high they never get hit and its op or
B) their eva is reasonable but if they get hit they die in 1 or 2 hits
Healing them wouldbe near impossible for this reason. They also can't have great def and eva because again then they would be op. They also can't have a tank running with the same dps output as a dps because then why bother having a dps when you could have 3 dpstanks and 1 healer because no one would ever die. All they can really do is add a tank with more dps utility which imho warrior already does this. Or add a tank with some healing capabilities. At this point I think any future tanks that get added are going to basically just be a reskinned version of the tanks we already have with slightly different skills.