I'm pretty sure a undead does not heal, if you apply decaying touch and heal. At least in the EA I think I tested it once and even got twice as much damage, from being zombie and being decaying.
Also not sure, if leech does heal you or kill you, if you are undead. They worked at Necromancy not killing you, but not sure how the state of leech is.
this... decaying touch + undead = twice the heal damage essentially making you an unarmored easy kill.. and there are often more enemies than you.. so they can afford losses while you really cant.
even with just the zombie trait i had tons of archers using first aid on me.
