whenever the job is listed as in RDM/BLM, the first one is always the main job, and the second is the support.

DRK/THF would have little power until 30 and in 60. But when they do they do alot of dmg. At 30 they get Sneak attak which does a crit when struck an enemy from behind. So go behind, Sneak+DRK power moves and a WEapon skill there, it will do massive damage. And Trick Attack at 60 makes it so the dmg you do from behind someone, will transfer all hate from the dmg to the person your behind therefore making it so you WONT get aggro so much.