With the unupped, creatures now deal ATK+1 damage so I'd expect a fair bit of damage to get in before they lose it all. Further more, you can't regain the lost HP without destroying your own shield.
As for the upped, that's a little more of a problem since it effectively has +1 damage reduction over the unupped and you get to heal (though it does restrict healing a bit). Still, it's hardly any worse than stuff like Fire Shield and those have plenty of counters.
The only problem I can see is that it has no element requirement.