Dark Knight

[Sylari]

My thoughts were more from a Tank standpoint

Given the Arcanist model I don't see a GLA or MRD based DRK being a tank class. The thematics of the job (the emphasis on offensive power and the 'hurt yourself for more damage' gimmicks) don't really line up IMO either.

I wholeheartedly say it would be Gladiator 30/Thaumaturge 15 to unlock Dark Knight.

I don't really see it. More recent incarnations of DRK (11, X-2, CC) from square have been favoring heavy weapons over the sword and board look of older dark knights.

My honest guess is that it's a DPS job crystal for the MRD. With Thaumaturge as the subclass and probably Lancer as the tertiary.