I mean, if Discover still gave a bonus to class based cards, I would rate this as Meta defining. You know exactly what type of minions you will be getting and have a high chance of making it happen.
This means that you will almost always get a 2 drop from the neutral pool because there alot of them and Discover is not weighted, so you will not be happy with this card.
I mean, getting an Acidic Swamp Ooze gives you a 3/5 on turn 3, but no battlecry. Meh.
Now, if you coin this out on turn 2, its a decent tempo play. It almost always will trade into an early minion for free and most classes wouldn't be able to kill a 3/5 on their turn 3. Even if they do kill it, you might go into the next turn with an empty board as they had to trade their minions away.
You can also get some horrendous choices too. Deathrattle minions would be best though, but not many that seem worth a card.
The card is so bad. I can't see any synergies to any every existing priest deck in hs history. No deathrattle, silenceable, big, value, whatever card. Maybe divine inner fire card, but then there are way better fitting T3 cards in classic.
It's not bad. The minion will be above the curve stat wise. A 3/5 or a 2/6 usually. There are also some great high rolls, like millhouse, injured tolvir, and amani beserker. Its discover which means you can dodge all the really bad rolls. The problem is there's not really a deck for it. Combo priest doesn't have the space and quest priest doesnt play for tempo. Won't see play unless some other kind of board centric priest deck shows up.
Priest have one big weakness: utilizing their Hero power early. This card always gives you a high health minion that probably survive. Having a way to use your power (or some healing) to have a board early is one of the biggest weaknesses of priests.
Won't see play in standard unless combo gets a ton of support, but then again I see divine spirit or inner fire getting Hof'd this april. The rez package would have to rotate, and this card would be rotating with it.