The problem is that if they did this, the content would have to be nerfed to compensate. Non-DPS slashing debuff, a damage down that works on Darkness damage(Darkness damage shouldn't even exist in the first place), and burst damage from Berserk are indispensable, the solution is not to nerf what's strong, it's to make the other choices more competitive.
PLD/DRK have nothing to compete with in an offtank position currently, but off GCD tank stance might make the gap a little smaller.
