Hearthpwn

Teched against control a bit by cutting Arcane Intellect, most of your value plays are battlecry minions so Brann is the most important card in those matchups. I feel like this list is slightly favored in the mirror and against Reno Lock.

Deck has a lot of 55/45 matchups, there is nothing commonly played that is super easy but also nothing that is impossible. Easiest relevant MU is probably pirate warrior where you win almost all games where they don't have a busted start, and if you both have a great hand you are favored going first and at a small disadvantage going second.

Aggro shaman is a bit harder than pirate warrior due to reach past taunts, but still favored. Reno mage, reno lock are about 52% favored, reno nzoth priest is slightly unfavored, egg druid is a bit unfavored, dragon priest is quite unfavored but still winnable (40/60?).

Other less common matchups I encountered in my climb were control warrior (VERY easy) and Miracle Rogue (slightly unfavored, but close).

Mulligan (when in doubt, assume they are aggro):

VS Aggro: Keep Mistress, Reno, Water Elemental, Volcanic potion, Doomsayer, Frostbolt, Flamecannon

VS Control: Keep Duplicate, Brann, Kazakus, Sylvannas, Kabal Courier