It's not an optimal setup at all but I use Kerria along with my four best attack debuffers (New Year's Ivy, Snowdrop, Oncidium Bride, Cherry) as the first squad on all of my whales. Fights tend to take awhile but any damage taken is minor and tends to be undone whenever Kerria's skill goes off or when the whale runs over chocolate panels created by having Lantana in one of the other squads.