To support Kerria thebests girls are, imho, girls with high (really high) attack buff. Girls like Halloween Peony are really good with both debuff and high attack buff on 2nd and 3rd turn. With Kerria heal and evasion it's almost a free +60% ATK. I guess we will have more girls like that in the future with rainbow promotion.
Or use Kerria-like girls. More Kerria, more power, more everything.