A healer who knows their business should know how to handle Living Dead.

Being able to stance swap outside the GCD is one of WAR's thing and probably a feature of it being the Damage dealing tank. PLDs stance swap requires a GCD too.

If Dark Arts cost less they would have to nerf its effects. Its balanced around not being able to spam it easily. One of the core mechanics of the class is supposed to be MP management.

The main issue I see with DRK is the overarching issue with Parry. Hopefully when they revisit the stat they will find a way to make it more workable.

All tanks have things they are better at. DRK sits around the middle between WAR and PLD with more in the way of defensive CDs and higher dps than paladins while having solid self healing abilities and stronger magical mitigation than either due to their CDs. They are certainly in no way the 'weak' tank Job.