As far as I can tell, healing can, and should be a viable option in combat for some characters, as long as it isn't a passive regeneration. I propose that if someone has a healing ability, it works much like charging, in that it requires them to do minimal movement, and with the possibility of being interrupted while doing so. Making it a maneuver that can be worthwhile if the opportunity for it arises, but generally, much like charging, not something you'd elect to do if your opponent is on the offensive.

TL;DR: Regenerating limbs while back-flipping off a burning car while shooting flaming balls of fire out of your eyes is a sure-way to ruin the give-or-take aspect of a fight.