Well, my characters weakness is easily exploitable with the right weapons: he heals himself by transforming arcane energy into matter or just resealing the bonds between molecues with it, so the cost is directly proportional to the mass of the tissue replenished or overall surface of the injury. Large cuts and deep punctures wont be as bothersome as a burn or ruptured organ.

Is it enough to balance out the capabilites of his power?