Essentially a 3 mana 2/4, that grows every turn, and pings? Not a bad balance, could see play if a highlander or control DH ever hit it off. There are some design issues with the wording you've used though. You would need to say it's a random enemy minion to make it clear it doesn't target (standard way cards are written), as well as you could probably just say it steals 1 attack and health, in the same way Ancient Void Hound does. So the text should probably be "At the end of your turn, steal 1 attack and health from a random enemy minion". Saves a lot on card text. While being a bit clearer.
But honestly I really like the way this card works. If blizzard ever printed this effect on these stats, I'd be happy to see it.