Hearthpwn

I hit Legend for the first time with this deck. Started playing it from Rank 4, 2 stars, to Legend today with only 12 losses. I do not have those tracker apps. I have listed them on a post it. Lost 4 times against Control Warrior, twice against Weapon Rogue, thrice against Undying Wall Priest, twice against Highlander Mage and Once against Quest Shaman.

Thank you for the upvotes and comments. First things first, I built this deck to kind of counter most of the meta decks that are prevalent in ladder lately. Let me tell you my thoughts on some of the card choices since the other ones are self explanatory.

Puzzle Box of Yogg-Saron - This card is very tricky. I included two copies just to increase the probability of casting it free from turtle guy or with Kalecgos dude. In my experience do not play this card unless you really have to. Meaning, your back is against the wall and you are sure you are going to lose once you pass the turn. This can turn the table around with some good RNG. 

Vulpera Scoundrel - Really good card for this deck. This serves as a "Tutor" when you are in need of a specific card or trap. The reason why this deck can hold its own against the more flexible Highlander variant, is because this deck out-freezes Highlander. It does not matter how big his board is, you can win by having more freeze spells. This card supplies you even more stall cards until you set up your board.

Luna's Pocket Galaxy - Broken card. This on curve gives you the advantage to win the game. 

Tortollan Pilgrim - Free spell! Since this dude casts a copy, that means it could be a third or fourth Frost Nova, or a Blizzard. Playing this guy on an empty board and picking Conjurer's Calling gets another copy of it AND two 8-Mana cost minion. Talk about value!

Mulligans

Druids - There are two variants that you may encounter in ladder. The getting famous Malygos OTK and just plain Big Baddies abusing the Quest. Against both, I try to mull hard to get my Mountain Giant and Conjurer's Calling. With the coin you can play it on turn 4, and turn 5 on first. Possible path the Druid will take against this is that they will sacrifice their Wardruid Loti to kill one, then floop the other one. which they will not be able to do on the same turn, meaning they can only kill one. Another way is using Oasis Surger, but, then again, they can only kill one. This plus your freeze stuff, mostly wins you the game. 

Rogue - This is a tough match-up but, winnable. I always try to mull for my Frostbolt, Doomsayer, Ray of Frost to deal with early threats, try the best you can to suppress until you can build your board while freezing his. Most of the time you can tell what the Rogue tries to do by the cards he plays. Out-value him with your cards. Arcane Keysmith into Flame Ward usually kills the pressure. Try to drop your Mountain Giant only if you can Conjurer's Calling it. Hope that you get at least one Taunt. More often than not, the Rogue can only kill one. Freeze his board and swing!

Warrior - In my opinion, this is the worst match-up. But, it's still winnable, more often than you might think. Mull hard for Mountain Giant and Conjurer's Calling. But, also take into consideration his removals. Shield Slam can be countered or baited by Arcane Keysmith. I know you may not be lucky in choices. That is why you must maximize Vulpera Scoundrel, so you can increase the possibility for Spellbender or Counterspell. Also, keep in mind not to over commit, Supercollider is a problem, so try to protect your Big minions by positioning a smaller minion in between them, or just Frostbolt him.

Hunter - Highlander Hunter is the most common you will face. He has high value cards and a very annoying hero power. I just mull for Luna's Pocket Galaxy to fight value over value. In the real world, mull for your removal and try to be present on the board. Do not leave a Mountain Giant alone. It will be dead by Deadly Shot. Another thing you can do is to get a big Zilliax swing by attaching SN1P-SN4P. Try not to get below 10 life, because Dinotamer Brann will crack his whip and next thing you know, you already lost. Just be careful and anticipate he always have answers to your board because that is why Highlander is so popular. Having this mind set against Highlanders will enable you to play one turn ahead, because you will consciously plan your next turn during your current turn.

Mage - This is going to be a boxing match. You try to mull for your early removal for his Acolyte of Pain and Luna Stargazer and deny him card draw. If you can decrease his hand size without compromising yours, you can win it. Basically, unless he Archmage Antonidas and Fireball you to oblivion, his win condition would be similar to ours. Big board generated by Conjurer's Calling. We win by winning the freeze war. Eventually, he will ran out since he only have a copy, while we can freeze his board for at least 4 turns. Just be careful not to sacrifice our minions to Reno the Relicologist + Barista Lynchen combo.

Priest - Just mull for your freeze spells, try to draw more freeze spells from Vulpera Scoundrel and Tortollan Pilgrim. Just watch out for that OTK outta nowhere. Prevent that from happening by baiting it with Arcane Keysmith and get a Vaporize or Ice Barrier. Eitherway, the priest will try to pop whatever secret you get, meaning he is wasting resources. Thus, prolonging that OTK outta nowhere. From there, you can basically tell that he has it and your next move is to freeze his board and set up your Big minions. 

Paladin and Shaman- The Quest Reborn pally is annoying. Mull for your freeze spells, until you can set up your Big Minions. Try not get damaged too much. What they are trying to do is completing their quest, and getting value our of the Robot Egg and Reborn taunts, both useless against freeze. Quest Shaman is pretty much the same mulls, but, easier to deal with than the reborn pally.

Summary

The ladder is infested with the above decks. This is how I try to beat them. I understand that most of the time it will not go your way, that is why we have freeze variant. Have fun and good luck.