Hearthpwn

I've been trying this deck out since I got a Confuse from a pack some time ago. I must say I'm completely in love with this deck! It's just so fun! The problem is that I'm short on Ysera and Eydis Darkbane so I used Faceless Manipulator and Djinni of Zephyrs instead... Do you think the latter fits the deck or should I swap him for the Dark Cultist? I feel like there's a lot of 3-drops already..

So far so good... took it on ladder and 6-1 so far from rank 18 down to 15.  I'll toy around with it more later and update my results.  See if I can get it below 10 when I have more time.  One thing I did was remove a Injured Kvaldir and added a Light of the Naaru instead.  

10/10 will try in ladder.

Indeed Dark Cultist is a good replacement for Eydis Darkbane, I chose the latter, because of 2 main reasons: FIrst, it is a new and flashy cards which looks good and needs testing. Second, and more importantly, it is a better card to take back board control, because there are plenty of cards to buff it (I think even divine spirit is a good card to use on her). Dark Cultist on the other hand is a win more card in a sense that it doesnt do anything the turn it is played and works if the opponent has zero board control/no removal, in which case you are already winning.

I also made a Confuse Holy Champion type deck, (although, admittedly i think yours may be better) and i think it has a real shot to get after the meta. I am REALLY hoping that the new Priest legendary does something crazy like raise your max HP to 40. That would make a deck like this GPW good.

With the reveal of Flash Heal today to go along with an Auchenai Soulpriest could be a really good addition... Especially since Auchenai Soulpriest + Circle of Healing is great vs Aggro. But you'd have another win condition with Auchenai Soulpriest and double Flash Heal. 

I'm not sure however, what you'd replace... maybe drop the Holy Nova and 1 Resurrect

Even without the Auchenai Soulpriest and Flash Heal, I think this could be a pretty good deck

Flash Heal is indeed a very interesting card, but I think it fits another burst priest archetype. While this deck focuses on Holy Champion and Confused high health creatures to burst down the opponent, a deck with Flash Heal would mostly use spells.

In order for Flash Heal to be powerful as a burst, a deck would need Auchenai Soulpriest double Mind Blast and Prophet Velen to have enough finishing power. Also it would require more card draw to get all the combo pieces, in contrast to this deck where all cards can be used on their own.

I actually also made a burst priest deck, where Flash Heal is an auto-include.

Good theorycraft deck, but lacks some big control minions like loatheb, dr. Balanced. Sylvanas etc.

You are absolutely right that in a control dominated environment those cards are mandatory. However, even with the joust mechanism introduced I think aggro will still dominate the meta and the current decklist should do better against it.