Once again considering Joan + Ares vs. Mordred + Raguel
BP buys you one overdrive turn on 1 opponent, Ares nuke does about as much damage as an entire attack turn, making it much easier to kill off the first ones.
Wind wave 2 has 3 Orbs, so you're just increasing it from 4 turns per OD to 5. Sure it helps, but on the other hand, with joan you have 5% more atk down, which also helps and tbh, if you lack the damage to kill this boss in 8 turns, then you're doomed for wave 3 anyways.
While this on it's own is true, if you can replace Raguel by someone way better, then Joan wins hands down.