You can certainly do the fight without ARCs, but ARCs' combos rely on distance, not direction, which is far easier to control. All physical DPS classes' damage ceilings are theoretically in the same general neighborhood, but it's easier to back up/move in than it is to find the moogles' butts/faces/sides. Melee-range DPS will also take more damage during the fight while killing the BLM and MRD moogles.