Hearthpwn

That deck is very versatile and it has everything: strong minions (stats, synergy), lots of draws, amazing synergy almost with every card and strong curve. The most important thing i want to say - you can and should change your secrets when you feel it. For exapmple, if there is a little aggro on ladder, replace that Explosive Trap. I will write some options in the end. However, this version i will definitely use at the start of the expansion.

Now let's walk through every card and i'll explain why it's here and how you should play them.

Fiery Bat: you can't find better 1 drop for hunter. Beast synergy, high attack and good deathrate. With some luck, Bat can kill almost every 1-2 drop from your enemey.

Kindly Grandmother: kinda the same card as Huge Toad, but slightly better. Here is why. Versus Warrios their starting axe can kill toad in 1 turn, but can't Grandma. Also deathrate is much better against brawl. For mages and druids it's hard to kill on turn 2 without a coin, so it's also better. Doesn't care about Doomsayer which is pretty popular. But the most important thing - it has amazing synergy with our 3 drops and the whole deck overwall. Combine it with weapon or Quick Shot and it's a 4 damage with alive minion due to deathrate.

King's Elekk: And again you will probably ask: why this and not toad. The thing is, in this deck you have lot's of secrets and just with them you can run out of steam pretty early. And remember that we have 2 important, hight-cost legendaries which you can draw easily. Overwall it's a good card.

Cloaked Huntress: Just that card and secret such as Freez Trap can win you a game. Just imagine that value: with Huntress and Cat Trick the value is 6 mana on turn 3! Even if the opponent remove our Huntress with Spell, we will get our beast. What is more amazing, that beast can become even stronger Houndmaster. That's 6 damage to the face baby. Oh, the stats of Huntress is also amazing.

Barnes: the stats of that card is decent but that's not really important. There is only 5 minion in the deck which can be bad summon - Elekks, Curator and Houndmasters. But there is 12 more to make you a huge value. Just imagine if you summon Savannah or Huntress (free secrets!). Even Azure drake can suddenly end the game for you. 

Houndmaster: nothing new, just good card with all those beasts we have. But now it's more great with new Cat secret.

Infested Wolf: A beast with decent stats and deathrate effect. Good target for Barnes. No reason not to play it.

Azure Drake: I say it one more - we need draw because of secrets! Even more we have lot's of tools for that +1 magic damage. And i'm sure you already figured out, but The Curator is one of the main reasons why we have that card. There is no better dragon card for that deck and we really need a draw.

Savannah Highmane: Just one of the best 6 drop in the came. Now even better with Barnes. 

The Curator: Do you remember those days, when you had nothing to play before your Call of The Wild? Well, problem solved! With that card you can forget about pure late game. Grab that damn Azure drake and now you have even more draw! And don't forget a beast and a huge stats of that card! Even without Drakes you can play it in amazing value.

Spells

 Quick Shot: Removal, finisher and can become one of your card draw due to secrets. Powerful combo with Kidnly Grandmother. And just imagine this card + Call of the Wild on turn 10!

Deadly Shot: Great removal. One copy is must have against druids and shamans. That card sometimes can win you a game. 

Kill Command: Finisher and removal. Don't afraid to clear the board with it, our tempo is much more important. 

Eaglehorn Bow: Clear the board with it, buff with secrets, smorc in face...

Call of the Wild: Best 8 drop in game, Nuff said! Now even better with Grandma.

Secrets

Explosive Trap: our great tool against zoo decks. Feel free to cut it if there is a little aggro on ladder.

Freezing Trap: don't remove that secret because of huge tempo it can deliver with Cloaked Huntress. Sometimes it can win you a game against shamans, druids and OTK warriors. 

Cat Trick: amazing secret which you can combine with  Cloaked Huntress and Houndmaster (that 6 damage is a huge pain). Also do not forget that enemey coin can activate that trap - it's really important. Many aoe spells such as flamestrike can't kill our cat because it activates AFTER cast. Must have.

What to change

Actually there is no much options besides secrets. Consider to change Elekk if you're a big Toad's fan, but i don't reccomend it as you already know.

The card that you probably wont need is Explosive Trap. So, how can we change it? The best change is 1 more Cat Trick. Just because we have a lot of synergy with that card. Another Freezing Trap can be an option too. 

Actually we can make it a bit control-like with N'Zoth, the Corruptor. With Barnes and The Curator you can make nice value with it. Well, actually even with 1 Savannah it's already enough. By the way, 1 more good target for elekk. But it's very slow, remember that.

And i think it's possible to change -1 Houndmaster +1 secret. You can even cut all of them because with Barnes we already have enough 4 drops and we don't want to summon them.

All of these variations i need to test in ladder. I will update this deck after release. There is so much need to be tested.

Mulligan and how to play

It's not really hard to play. Just remember your combo with Cloaked Huntress and you will be fine. Don't afraid to keep her in starting hand with coin and secrets. But in most of the time keep Fiery Bat, Kidnly Grandmother, King's Elekk and any 3 drop. Against druid always keep Deadly Shot and maybe Freezing Trap. Overwall you want to play on curve, make tempo with new cards and make smart trades.

That's my first guide and probably the biggest text i wrote in english. Feel free to sent PM if you wanna change my mistakes. I can't wait for Karazhan release and i'm pretty confident about that deck. It's powerful, easy to craft and play. Hope you enjoy it and thank you for reading!

Btw i'm not sure if i should call it tempo or midrange, so let me know what you think!