Like someone said, DRK can go in any direction and the mind set is too much like FFXI. If we went through the FFXI route, we would basically have a job that has what WAR and DRG already have.
There are plenty of reasons DRK can work on GLA or MRD, but in my opinion, I think it would work better on GLA. Not just mechanics sake, but lore sake also. DRK opposing PLD has a ton of potential and I think SE should take advantage of that.
But I think I can better form an opinion on how DRK could adapt once 2.0 hits.