Well, generally speaking, 10 HP is about what you get from killing a single trash mob. And it's giving you that every 1-2 seconds. That's... quite a lot, if you think about it in those terms. That's like chaingunning some mobs while just standing there.
I could see maybe doubling the rate if it's just too painfully slow, but I don't think that it should be a percentage of health or something that is super much higher, honestly.