Bad. Healing cards suck in general. Greater healing potion mainly sees lay in Big Priest, which can't use this because its a minion. Otherwise, if it is used in control priest, it needs to playable by turn 5 or 6 against aggro to delay for a board clear. If control priest makes it turn 10, either its won, or 10 healing won't matter much.
Feels very similar to the Priest C'Thun card, Twilight Darkmender which didn't end up seeing ANY high level play, even while the game was pretty aggressive. Comparably this card doesn't require you to build around it and has a much better stat line but also doesn't work until turn 10. Healing currently isn't very valuable right now since a lot of the top decks are really slow and tend to kill you all at once so I don't think this card would see play in any current deck at the moment and I don't think Priests have much of a problem with health once they get to turn 10. That said the stats are very nice.
Premium stats, pretty good effect, and helps most after playing Shadowreaper Anduin since you will need more turns to finish off your opponent, and this healer synergises with the hero power since he's cheap
And good news for Tempo Mage haters out there : This card plays around Pyroblast and only for 3