My two cents about it:
Since Debuff Teams work best with Life Leech Girls (Kerria, Aconite etc.) i prefer Debuff Girls with Skill.Act.
I like her 12% miss for enemies though. Good Combi with Kerria's Evasion. If you have other methods to boost your Skill Act. outside of the Debuff Squad (Lantana Summer Festival for example) Sedum could be really good. I like White Tulip more cause she also has 12% miss for enemies and she has Skill Act.
Shield is good but i think it's more important in Counter and Crit Teams.
Hmm now that i think about it:
Kerria, Aconite, White Tulip, Sedum, Snowdrop is a strong team. White Tulip and Sedum basically buff Kerria's Evasion to 74% after the first two turns due to 24% Miss Chance for Enemies.
Throw Lantana (Summer Festival) in another team and you still reach x2,06 Skill Act. with your Debuff Team ;D