My plan to use Kerria would be in debuff team with
OnciBride
Snowdrops
Epidendrum (swimsuit ver.)
Stock
Kerria
This team geared to outlast boss. Nothing more, nothing less. After turn 3 the team gain additional 60% atk and every time Stock got hit, prepare for the world of hurt with 35% damage bonus. Debuff is not at 70% capped however.