Hearthpwn

At first blush this deck looks horrible, It looks like a weird janky midrange priest deck. On some level it is in fact a weird janky midrange priest deck, but the deck is saved by the fact that it can do otk combos and also generally runs a lot of burst. 

It basically uses midrange stuff to get an advantage against control decks with a bunch of healing and then burst them down with Mind Blast and Holy Fire. The combos in this deck are not consistently strong enough to work without a little bit of damage from midrange minions surviving and going face a few times, and the midrange shell is not strong enough to work without some burst considering how weak priest is as a tempo deck, and how strong control is right now, as the meta changes this might change but for now I think this is the best way to run this type of deck.

Now on to the combos:

30 damage: Radiant Elemental Radiant Elemental Tainted Zealot Mind Blast Mind Blast Mind Blast Mind Blast Holy Fire

28 damage: Radiant Elemental Tainted Zealot Tainted Zealot Mind Blast Mind Blast Mind Blast Mind Blast

20 damage: Mind Blast Mind Blast Mind Blast Mind Blast 

or

Radiant Elemental Mind Blast Mind Blast Mind Blast Holy Fire

or

Radiant Elemental Radiant Elemental Mind Blast Mind Blast Shadow Visons Mind Blast Shadow Visons Holy Fire

15 damage: Mind Blast Mind Blast Holy Fire

or

Mind Blast Shadow Visions Mind Blast Shadow Visions Mind Blast

This gives a lot of versatility depending on what you draw, which is important since you don't always have time or resources to pull out a full otk. This deck is very high skill, because determining how to sneak out lethal and when to commit resources are both very important to winning with this deck. I have had games lost because I did not notice that I had 24 damage in hand for 6 mana with 6 mana left, and my enemy at 23 health, so I used hero power on my hero, and then the enemy healed up to 27 and I never drew the cards to get lethal after that nor was I able to get any extra damage on his face to get in lethal range. Always count lethal in every turn just in case. 

In terms of mulliganing, you basically want to mulligan away cards like Shadow Visons, Mind Blast,Tainted Zealot, Coldlight Oracle, and anything over 3 cost. You want your early game minions in hand so you can hopefully curve out, and then start drawing aggresively for burst to finish off the opponent. If you don't have any one or 2 drop minions in hand throw away Kabal Talonpriest, but otherwise you want to keep it as a big tempo swing allowing you to trade a minion and keep it alive afterward. This is especially important since a lot of your minions have powerful effects you want to keep on board for as long as possible. 

So far this deck does decently against control decks, which are currently a majority of the meta, but against midrange and more aggresive decks it is really a race, as you have less board presence than them. 

Edit: I removed Potion of Madness and added in Fire Fly. the reason for this is that it allows the deck to consistently play a one drop minion, which in turn allows it to snowball on board more often. Plus against aggressive decks, consistently being able to trade minions, is better than killing two if they overcommit. Another problem I faced was that Potion of Madness occasionally made my Shadow Visions slightly inconsistent, Because occasionally I would not get the option of either of my burst cards, and that is the only thing you want to pick off of Shadow Visions