Everyone is talking like it’s an either/or between Chacha/Bunyan/Spartacus. For easy farming missions it’s quite feasible to use all three of them in the same party. I have a party with:
1 slot) Chacha with her first skill maxed, equipped with The Imaginary Element
2 slot) Paul Bunyan equipped with Holy Night Supper
3 slot) Borrowed Waver
4 slot) Spartacus equipped with Kaleidoscope
On first turn Chacha uses her first skill, Waver uses all of his skills (with the crit one used on Bunyan), then order change Spartacus in. And boom, you can use all three of their NP’s to clear the 3 waves. Chacha has to go last for wave 3 because of how her charge skill works.