The formula looks pretty close. So at level 20, a character with 5 Constitution would have in the ballpark of 1461 HP.

It also fits the Level 27 Zixzax, who has 36693 HP, which means he has 20 CON.

If monsters are supposed to follow the same rules as PC's, that means... I think I'm starting to see why spell damage is scaled based on your ability points in a school, and not points spent on improving individual spells/skills.

I don't think this game will be wanting for weak bonus bosses.