1 HP is broken, especially in doubles, where you can give Shedinja Sturdy. Basically invincible, even to super effective attacks. You're forced to bring in weather or status to beat it. Wonder Guard is also broken, but less slightly than Sturdy Shedinja. It's not hard to use Shedinja at all (all you have to do is learn how to predict and since you don't have to worry about any other attacks besides super effective ones it's not that hard to tell when to switch out) so it needs to be banned to Ubers.
"Bored." --TheFightingPoly, 2014 Ask for FC if you truly need it.