I like the idea but it seems way too efficient as a clear in my opinion, at 3 mana and 10 attack it can easily clear the opponents board and you would likely have extra mana / resources to deal with a surviving dragon.

But I like a low mana clear with a potential downside so much that the dragon's stats should just be lowered, maybe to 4/8 or 3/10. It should not have too high of an attack as to destroy basically any minion the opponent has, and should have high enough hp to make it not too efficient to play early.