Ares also have the ability to burst by turn 4 if you get the RNG right.

BP stops being relevant for AQ4 when you have reached certain grid level. You'd prefer for boss to OD earlier because you can do a lot of damage to push boss to rage in 3 turn, so eating non rage OD is the better option than rage OD.

What often overlooked is that Joan also has a DA buff that have a quite decent proc rate.

At the end of the day, whether you run Joan + Ares or Modred + Raquel depends on who you have for next 2 slots and where your grid is currently at. Do I have enough damage to not need BP so I can run all SSR lineup to maximise my burst damage? Do I not have enough damage that I need BP to reduce how often I take overdrive?

Team building is often regarded as simple exercise. It's probably not as simple as many people would've liked.