Don't forget that DRK can use their offensive and defensive "stance" at the same time as well, making that 20% decreased damage into 5% instead. Mp is really a non-issue since you both got a CD for that, and will be using your "get mana back" skill as part of selfhealing and -int combos.

Also, why is the PLD DoT skill the only one hidden behind a combo?

@alimdia: I think he ment the normal cross-class cure, not clemency. Clemency is so situational that it's pretty much useless, not to mention that it costs too much resources (time/mp) for what it does to really be worth it.