Yeah, believable is probably a better word for it than realistic. So here's my last sentence with new and improved wording. :P

"I always thought it was a great way to make it feel more believable and not just accept it as a mechanic which exists outside of a game's reality."

But yeah, just calling it "luck regen" instead of "health regen" was brilliant in my opinion. It didn't change anything in the game, only our own perception and that was enough for it to make perfect sense.