Actually no, decaying touch only affect healing spells or potions, no all healing.
I am not 100% sure but really think Healing from higher than 100% resist in an element still heals you with decaying touch.
Healing from necromancy spec or skill (mosquito swarm, pool of blood) still heals you with decaying touch so you literally have nothing to stop it.
I was thinking how this mechanical design would work. I didn't test it, but if you say decaying touch isn't useful in this case, I really think retribution should be redesigned. Not necessarily physical damage, but some sort of "true" damage. This means it couldn't be resisted.
For example, if someone hits you with a physical attack, they'll recieve unresistable physical damage on their physical armor, if any. If they hit you with a fire or poison spell, they should take damage on their magical armor, if any, but an unresistable "neutral" magical damage.
Maybe they should do something about two characters with retribution hitting each other too, so it stops the "boucing" damage. Maybe the retribution damage shouldn't trigger the reciever's retribution, because it becomes a cluster of numbers whenever one hit each other.
