I've played a handful of characters now, with varying levels of endurance, and it struck me as odd that the point where they would stop regenerating health would change.
Something just doesn't seem right about that value being relative. It takes some of the edge off whatever advantage you get with greater endurance relative to the species.
Admittedly, I wouldn't want just a single value for each member of the race to be the point where they stop regenerating, but I would like the regeneration value to hold a bit closer to such a value, instead of the absolutely relative function it is now.
Since it is a percentage, and you only lose HP in hard numeric values, there is still an edge to having more HP than someone else. For example, if you had 150 hp, and someone else had 75, after taking 50 hp damage, you can regen fine, while the other has to go crawl in a hole and sleep. Of course, these numbers are completely made up and a bit extreme, but I'm sure you see my point.