Okay, let me see what i can aid you with...
First, that Snow White is an great sub for your water team, an unbindable bind healer with heartmaker AS AND more bind clear, also with really solid stats for a 4-stars, til this day i wonder when will GungTroll make their UEvos.
Second, your should pay more attention to that Naga too, Echidna is a great card for midgame and even late-ish game due to her Active, she's the only farmable delay that i can remember.
Third, if you feel like you can do it, try farming for a Armadel, she's is an ok sub for Verdandi, having an Synergising and reliable AS, same att. and subatt. , and 4 OEs,which aren't much but will still help.