the need for 3rd tank class

[ApolloGenX]

WoW Deathknights had CD rotation options... it didn't work- why rotate CDs when other tanks passively mitigate? They ended up redesigning them to make tanking easier.

Overly complicating a class to get results on par with others makes for a poorly designed class- not an interesting or played class. See WoW warlocks for example.

Currently, the only idea I would have for a new tank class would be magi-tech based... with passive mitigation via "tech gear" (basically like current mitigation gear but with clearly tech graphics... and skills that deploy tech - such as instead of taunt, have a hypnotic beam. If nothing else it would be clear who the tank is taunting via the beam. Players seem to like shooting beams.

Instead of a plain tank CD, activate a force generator that puts of a visible field....or armor that deploys and covers the body.

Since tanking is pretty bland, you could spice it up with interesting and unique visuals... that might help. I could definitely see some really cool tech based weapons being a draw for players.