Of the new shards I've gotten so far, this is the one I've used extensively, and so I'll make a few comments:
Sacrifice is definitely a powerful shard, but, at least in the deck I'm using it in, it's not the complete gamebreaker I was worried it might be. You have to be careful to time when to use it; if your health drops too low, it's a dead card, plus YOU will be dead soon after :p Play it too early, however, and you either waste some of the potential for it, or worse, just take damage unnecessarily from it. It also combos nicely with shard of divinity; play divinity first to get your health up to where you won't die, then drop this.
It's pretty mean in pvp; I just took it into pvp2 for the hell of it, and ended up against a firestall. Once I had my opponent poisoned enough, I played shard of sacrifice, and there was literally nothing that the opponent could do about it. I don't think he/she had seen the card before, because they tried to OTK me the next turn with fire lances, and it just healed me
(or else they knew they'd lost and decided to just give me free electrum)