Dark Knight DD or Tank

[Fantasia]

You know that they could add greatsword to GLA right? That was the original intent of the GLA, to use sword+shield for tanking and then greatsword for DD (similar to how WHM and BLM can use both one handed and two handed weapons). However, greatswords never got implemented. We don't know how GLA is going to change in ARR, so it could be very possible for DRK to come from GLA.

As for what role DRK should perform, I would say it should be a DD/debuff class (recall it has had abilities that weaken the opponent while strengthening themselves).

Adding a secondary weapon to classes would mean that it'll be more difficult for SE to come up with other classes as the weapon choices would fall rapidly. I don't think they'll do it (I hope they don't) since they want people to spend time levelling with as many jobs as possible.