I don't see a huge problem with the blessing effect being permanent... this duplicates the Graveyard's effect, except the attack boost is applied to an already-existing creature rather than creating a new one. On the upside, that means you can bypass damage reduction shields better and survive Firestorms, but on the downside, it's all your eggs in one basket.
The Fractal Spark combo is the only one I see being remotely broken; this could be fixed a little by dropping the boost to +2|+2, but that may not be necessary. It's a duo combo involving Fractal, which is getting a cost nerf soon... and Fractalspark-Vulture combos can be just as strong, even stronger if you get more than 3 Vultures out.
The question I always get asked on my cards: do these stack? If you have two in play, will your creatures receive +6|+6?
