I disagree with this. It's an advantage with no disadvantages. It would become a must for spars(unless you disable it for that) and possibly required by elitist gangs. Maybe if you put some kind of debuff in it as well such as lowered movement speed it would be ok.
It would be fair if you can use it out of combat and have the buff go away upon getting hit or hitting someone.
Another idea is to just have people heal slowly over time when out of combat for 15 seconds, so those without houses and beds can heal without running to a hospital or purchasing sodas and all that.