One argument at the moment is that healers who don't know how living death works cancel it before it gets used. If it was changed the way that healing harms you, we'd still have healers who have no idea how living death works. Except now, the worst they do is heal you (which, if they have time to do so gives the ultimate end result, you're alive) while with the zombie stuff, they'd actively kill you and then moan about you taking too much damage.