I prefer to think of it as being like Glen Cook's Black Company mages - some of the Taken survived being hanged, beheaded, emtombed for a thousand years, smashing into a castle wall at about 100 miles per hour (with no seatbelt, air bags, or, mmm, car
), and worse.
That's what I think of, when I think of human mages attempting to become gods. Not someone's grandmother who could be killed by 3 good papercuts.
That said, I also have some reservations about the human mages hit points, mainly because it seems that if an arch-mage has 21 hit points, a giant mage-godling should have more than 50% more. It's a scaling problem; not that the Skratti really needs improvement, but that it seems it should be substantially harder to kill than a crone.
So - maybe a couple built in magic items might help, in place of the hit points. Ethereality, air shield, lightning immunity, regeneration (on the druids especially, who also might still get higher HPs). No uber items - as a game went on, you'd quite possibly want to upgrade the items, but enough to give them an initial bonus. (Albeit I don't think pretenders / units can be modded for things like misc items.)
Anyways - the HP increase for humans isn't bad; for instance, it makes it rather more difficult to nail a human pretender with a single Seeking Arrow, which has always been an issue with sending them out site searching.