Few Final Fantasy games that had DRK in them gave them a huge HP pool, because they also had abilities to draw from their own HP to add more to damage, and I'm sure despite being a Tank class, XIV will have that too (and I'm sure people will freak for the first few weeks DRK players use them in dungeons lol).

What I'm trying to say is, DRK doesn't have to be a meat shield style tank. His form of tanking could very well be "Kill it fast, kill it hard, kill it before it kills me" (not aimed towards the party, mind you, more of his way of fighting), while PLD's are more of the "Ha, shield! Ha, parry! Ha, defensive skills all staked! Take your time guys, I'm good!"

Just my two gil. What ever SE decides to do to make DRK an efficient tank, everyone will adapt to it, and as a huge fan of the DRK class, and still feeling regret from never capping my DRK in XI, I will certainly having fun playing this class. (had to break my reply up, was too long for one post apparently).