Firion has all the White Magic so he doesn't have a lot of Stregnth to begin with. But that's more than taken care of with Gus and Leila and Maria has Holy 6 and Ice/Fire 5 and Bolt 4, so I don't really have a problem doing damage. It's awesome that Blood Sword drains HP, but it's soooo weak, I'm not sure it's worth it.
Also, Esuna 5 can cure anything right?