Originally Posted by
Absurdity
For warrior and gunbreaker it is a dps increase to use your aoe combo on 2+ mobs.
Keen Edge -> Brutal Shell -> Solid Barrel = 3 GCDs for 900 potency total, Demon Slice -> Demon Slaughter = 2 GCDs for 400 potency per enemy hit. So let's assume you do 6 GCDs with atleast 2 enemies. Your single target combo would deal 1800 potency in damage and your aoe would deal 1200 potency per enemy in the same amount of time for a total of 2400 potency in dps. It becomes a bit more complicated if we factor in cartridge spenders but generally you want to prioritise your Gnashing Fang combo for 1-3 mobs, at 4+ mobs Fated Circle will deal more dps.
I'm not too sure about paladin or dark knight but even there you can safely assume that at 3 or more enemies your aoe will deal more damage in total. This obviously changes at lower levels when you only have access to 1 aoe ability with relatively low potency.