Interesting.
Now you have Fenix chan, so the ressurection thing is still big deal in those numbers, but yeh I suppose a 20% dmg debuff for a beefy boss might make the difference between one shotting someone and having to attack twice to kill em.
I shall give this a long thought and browse through the whole FKG list again to see which debuff girls would work out for me since I might slightly alter the rest of the team if necessary to accomodate the idea of a different skill type girl.