I would like to say that Kerria quickly drops out once you have to fight 3 enemies, but my Kerria -70% team would argue otherwise. The mistake a lot of people make when it comes to Kerria is that she is not a character you can just pick up and run with. If you do not have the units that make her... well Kerria-level broken... than dendro, Frita, and the like are much better choices...