When would you take DRK over PLD or WAR?

[SpookyGhost]

As a nin I don't like playing with drks, also warriors have way more hp.

That's an illusion. WAR's have 25% more HP (and 20% more HP recovery from healing spells), but take 20% more damage. Everyone takes the same % amount of damage, but WAR's get healed for slightly less %-wise.