i think you are looking at this differently than i, with this being a permanent, it is subject to pc/removal. if it were a spell, it would be irreversible. additionally, playing more of your own creatures will result in watering down the effect. the card itself will never kill any creature, and high hp creatures, while subject to the most hp loss, will still be likely to survive a cc attempt or two.
and i rather like this in combination with voodoo doll, now that you bring it up. it would probably only add ~20hp in most cases, but it still makes voodoo doll more usable.