Then where would Dark Knight fall?

They released that art that looked like DRK armor, so it IS coming, or so it seems.

Dark Knights throughout Final Fantasy have used Sword&Shield, Great Swords, and Scythes.

I'm pretty split, because I can come up with logical reasons for DRK coming from Gladiator, Thaumaturge, and Marauder, yet I have no way of knowing which I should level. Hell, I can even connect Lancer to DRK.

Confusion!