I think it's just boring. Rogue had a similar card, the onyx spell stone from K&C. Priest already has plenty of board removal, and I feel like the developing team could have done a better job finding a more interesting effect, like gain control of 3 random minions or something with bit more flavor. In terms of critiquing the card power, it feels pretty strong. Its like Shadowreaper Anduin, but able to deal with minions with under 4 attack.