Shoot, I did forget the "Erase Event" on Formidos. Will get a patch out for that ASAP. (FOEs from Etrian Odyssey do go away when they're defeated, and they're the direct inspiration for the Formidos, so it'd be odd if they didn't.)
The boss's AI skips its Fire attacks against Brill if she's Fire-resistant enough, and also skips against Aida if Brill has the Friend Defender effect. I did forget that Barbaric Blow lowers Block, I'll add that to the Check data real fast.
Holy Water doesn't produce a bright light, but it does deal bonus damage against the boss.