I have had my DRK lv up to 38, so I could be wrong on something but so far, my experience with DRK are, speaking from a long period tanking:

1/Similar tanking style with Paladin for group tanking as in, spamming Unleash ( in case of Pal: Flash) and use Syphon Strike combo to regenerate MP (much like Riot Blade combo with Paladin)
2/ Use Blood Price as soon as they are off cool down when tanking to regenerate more MP.

And I found myself having no problem holding hate