I'd say dragoons and monks are pretty close in terms of difficulty, and as Allyrion said, the difficulty is overrated. But monks have the most positional stuff in the game that they use constantly, dragoons have two, and BLM has like none and are ranged as opposed to drg and mnk which are both melee. so i have no idea how you came up with blm>drg>mnk in terms of positional demand.