I'm not going to lie. I'm disappointed. There's a LOT of thematic sacrifices they'd have to do to make DRK work as a tank, and I'm not too keen on the fact they took what some of us suggested for samurai and gave it to DRK. Nevermind that a guy in heavy metal armor (DRK) should not be able to dodge worth anything while a guy in laquered/wooden armor (samurai) should since the latter is less burdened by equipment weight.
That said, yes, Dark Avenger was Lineage II's best tank and that was basically a dark knight in everything but name (well, they did have their summonable pet panther). They did have defensive cooldowns that were in part shared between them and paladin (Majesty). There's also WoW's death knight to take into account, except that one of the main mechanics from DKs was given to warriors (active mitigation derived from one of their attacks) to help make them viable tanks in endgame content.
With this in mind, you can't copy-paste Death Strike => Blood Shield on to DRK because WAR effectively has that mechanic. The other stuff was damage mitigation buffs (Icebound Fortitude, Bone Shield) but that still leaves a key mechanic. Full on drains have proven to not work (AKA the original reason why WARs could not tank coil when the game launched), so they'd better have something else planned to help DRK ease into the role, or we're gonna see a repeat of that whole mess.
PS: Considering how terrible the armor for DRK in the FFTactics rerelase was, please for the love of the twelve give us an outfit based on Gafgarion's outfit from FFTactics.
PPS: Since they're not giving it a base class (horrible implications there), does that mean I'll be able to make my retainer a DRK come expansion?