Without knowing the actual system yet, the one thing that I'm concerned about is that you clear the dungeon - get your chest, and nothing drops for your preferred job; no-one greeds because they want main job equipment first, don't want locked out in case the desired piece is in the next coffer, and the run is wasted. This happened to one of my FC Coil goups last night, nothing dropped for a "main job," for the first few turns.