Hey thanks, glad to hear you liked it! Saves should be transferrable, next update will be adding some new mechanics but I don't think that'll mess with saves.
Banshee is meant to deal very little (if any) damage from attacking. She's arguably the most powerful, but that's balanced by her low defenses and reliance on MP skills. Her Attack scaling will be more noticeable as the party levels up, but her direct attack will always be pretty low. I am considering tweaking combat a by lowering enemy defenses while raising their hp a bit, just so the whole party can contribute to combat more often.