My guess would be it's going to end up being a very HP-centric Tank:

2 stances - One that drains HP from a mob and another that drains your HP to increase damage
High damage move that sacrifices a percentage of your HP (the higher your HP, the higher the damage)
Probably some sort of perfect dodge ability that only procs once your HP goes down to a certain level

I will be really interested to see how they implement it.