Ok, was down to just Chewy and my 5 man team + Ally.
Chewy goes full-on berserker mode and starts firing off 2-3 shots per turn, dispelling all debuffs (heal immunity & slow primarily), and giving himself taunt & heal. Oh, and his turn meter goes up so fast he does this every other turn. I finally hit auto since it was clear he was never going to die and watched him slowly whittle away my team.
Oh, kill Lobot first, or you'll be sorry.
It's 5B that is impossible...for me now anyway.