2, There will be a shard for ALL the elements, and one of those may counter this one perfectly, or be powerful in it's own way.
In fact if you read the chat logs, one already does..water's shard will probably be one that freezes permanents. Also any other form of permanent control would work against this.
Freeze it, steal it, explode it, pulverize it, or otherwise deal with it and you have an easy win. Unless of course they can play this, nova or tower to gain
, and then PA it all in one turn. Even then, unless they also can "damage" themself somehow, you can still play holy flash or antimatter your creatures or find some other way to "heal" them for the last 1hp they have. So at least half of the elements have a direct counter to this by either removing the effect of the shard from your opponent somehow or by simply "healing" the last hp to win directly.
Not saying this thing won't necessarily be proven to be OP at some point, but it will need to be tested carefully first. It is far from being as obvious as it may seem from just a quick look at the effect of the card.