40 hp makes direct damage a lot less effective, even at that point. Mooks really can't hurt you, you don't really hit any less because there's so many ways to boost attack rolls, and that soaks most hits from monsters. Sure, it may only be one or two a round, but it's enough. Especially when temp hp always stack unless it's from the same source. Getting more free hp each round than a cure critical isn't bad. It's enough to matter for most games, where any frontliner that qualified would be taking it and frequently using it, resulting in forcing a DM damage escalation. It encourages rocket-tag, basically.