I feel it's going to come off of gladiator or lancer. I doubt they create a new class for DRK. Paladins are knights and so are Dragoons so i'm sure it will be one of those. Whether they make DRK a tank or a DD will determine which one it derives from. It should be a DD if coming from GLA to be opposite of PLD and a tank if coming from LNC to opposite DRG. Personally I think they should be a tank this go around. It should have a lot of life absorbing abilities of course, and have something like a symbiotic ability. Where the damage dealt from one mob actually happens on whichever enemy you use symbiosis on.