The thing with WS in later stages is, you need that BLOOM on your girls. The raw stat increase is what you need for you WS.
I´ve been playing this game for a damn long time and just got my ass handed to my on the last stage of the new WS mission.
Unless you whale and have tons of 6* ov every color, your 5* of which most will be event ones anyway, wont have the stats to beef up the WS attack high enough for smooth sailing.