I love DRK and WAR. DRK is great with magic damage and in general has better damage mitigation than WAR but higher DPS than PLD. I think its meant to be the in between of the tanks the more generalized tank. I like having the INT debuff being the second class that can do it. I don't see a need to change the abilities though I would like to see an Equilibrium type ability for MP gain for when they are in Grit