Problem is if you heal using heal orbs, the heal applies AFTER damage, which is good for Goemon but not for full HP leaders. So if you heal and attack at the same time, even if you heal to full you get no bonus and likely you'll get hit by something and not be full HP again. (i havent actually tried this but going with how goemon works im pretty sure thats how this works as well)
Metatron at least has a heal ability which allows her to possibly heal to full and strike for full damage and Zeus can use any sub he wants while Koryu is stuck with dragons who cant do anything but attack things.
Oh Man Isis, Echidna, Susanoo, Koryu, Rkeeper would be legit as fuck
On bosses pop Koryu and Echidna, then attack for 3 turns, then pop Susanoo, then after 5 pop Rkeeper. Then if Echidna and Koryu are max skilled they'll be up again.