so combining those three graphs I'd say erebus starts off with fairly poor survivability in terms of ability to soak hits, which would be a combination of armour and regen,and with middle of the road hp (3rd out of 6 demigods)
His regen from his base stats remains middle of the road throughout the game, his hp remains fairly close to oak, his armour gets a lot better, making him more survivable fairly rapidly, but he's still not really able to tank out any fights until level 11/12.
Some people reckon the game rarely goes past lvl 15 so try to remember that for some cases the game is virtually over before his stat armor starts becomming an asset.
His skills however make a big change to that picture, allowing him greater regen, a mechanism for healing, and two mechanisms for getting out of sticky situations. Three out of those four things are quite mana dependent though, maybe I should do mana and mps graphs as well, but they will have to wait until tomorrow