I just throw down Lancelot at everything with mlb Damage CE. His (Merlin+Waver empowered) crits can down any mid-wave boss enemy between Camelot, Requin, Rakucha, etc..

Or I suppose first wave boss enemy if we're talking about Camelot....

So, BNPB/BNPA+X, or NPAA/NPBA+X, gets the job done on those waves. Merlin also can 1-Shot the weaker mob enemies when they come, somehow. Between his charge, Mana Loading, Merlin and Waver's constant charging, and Arts Crits for gauge, he refills his bar super fast turn by turn, if not outright repleted (prioritize Arts Chain if available on inopportune turns).

Downsides, it's not FGA friendly and it takes multiple turns going for max QP drop, sans Damage CE. Upsides, I only need 1 comp for all nodes and it's not mind-numbing. It's just so satisfying seeing the Coins go down just as quickly as they come in.