Yeah the devs are crafty. On some EX-Aqua-Shadow Maps the enemies attack first on others they don't. Baiting us to purchase as many girls as possible for all different kind of situations.
I have Kuko myself and i can say her Shield Ability is a godsend against Saboten Twins. I basically only need my Crit Team to complete that map (2/5 of that team aren't even ampuled).