I have had a lot of luck with this deck.  I cannot tell you the exact win rate because I mostly play on my mobile and don't have replay.

Anyway, I have been using this regularly on my monthly rank climbs and I think because it is a genuinely off-meta surprise deck, that not a lot of decks can play around it easily.  Just as the name suggests, this is a mid-range deck.  You aren't going to have a heavy early game other than getting set up.  The thing that separates this deck from other mid-range decks is that it has the ability to outpace and outlast other decks.  I have a positive win against Rogue in general, Murloc Paladin, Priest in general, and every Highlander I encounter.  Really, the only times you would realistically get dominated is if the RNG is against you. 

Starting the game, you really want to make sure that Boggspine Knuckles in your hand.  It is the key obviously as this is an Evolve deck. Having it equipped also means that the Dread Corsair comes out free.  Played in correlation with Desert Hare means that you can recover from a board wipe or against another deck that does the same. I put in two Hoard Pillagers so that when you use your knuckles to attack and evolve your squad, you get them back and swing right away and get a 5 cost minion.  The Bogstrok Clacker is also super handy when you have a Devoted Maniac and another minion on the board.

The biggest pieces of advice I can give you is:

1) Do not deplete your hand too much in an attempt to set up a killing swing next turn.  All too many times  have done this only to be met with someone countering it really well. I usually go for 3-5 minions on deck at most unless my opponent has 0-2 cards left and I've seen them play their tactical cards already.  Over committing and early celebration has brought the downfall of better people than me.

2) You usually do not want to upgrade Galakrond, the Tempest all the way, but it is situational.  By upgrading him all the way does give you a 5/2 weapon and 2 8/8 rush elementals.  HOWEVER, this is a Mid-Range Evolve deck. Going big and heavy will leave you with a 5/2 weapon for the Hoard Pillager to grab instead of the Boggspine Knuckles and potentially make your 8/8 turn into a Mogu Fleshshaper that will probably die before you can Mutate or evolve it.

3) Trade when you have to.  Because there are cards that help to replenish your minions on the deck with multiples, such as Desert Hare or any of the invoke cards including the hero ability from Galakrond, trading is almost always an option to control the board.

Vs Strategies and Muligans

Pretty much any game, you want to have a Boggspine Knuckles in your hand.  Yeah it is a dead card for at least 4 turns, but having it means that you are ready to start evolving turn 5.  And with the Hoard Pillagers, you can mass evolve 8 times.

Vs Warrior - This is usually the hardest of the match ups simply because it can come out so fast.  BUT, you want to use the Invocation of Frost to hold back their attempts to swing and use the elementals to drop the early game.  You probably won't be able to mass evolve until turn 6-7 because you need to keep their attacks to a minimum.

Vs Priest - One of the few times you won't necessarily want to keep a Boggspine Knuckles in your opening hand.  Usually, this is going to be a long game.  Especially if you see the Activate the Obelisk.  All you are going to do is set up for a 4-5 minion swing at once and use the early parts of the game to kill off things and not attack and give them the option to heal and complete their quest. This will most likely be the time that you upgrade Galakrond, the Tempest all the way.  Watch out for Plague of Death, which is why I say never over commit the boad and keep a Desert Hare ready to drop and evolve.

Vs pretty much any Highlander build - The waiting game is on your side.  There is enough minion trade to keep their earlier threats to a minimum and your mid-long game is going to end them.  Just like with Priest decks, you have to watch out for The Amazing Reno.  The mage will wait for your board to be filled and then drop that and you have to start over at square one.

Vs Demon Hunter and Murloc Paladin - pretty much the same strategy as with Warrior.  They are going to come hard and fast.  But since you can recover with quick drops that can have rush and potential to evolve, your trades are going to be better and you can get your weapon back relatively easily.

I hope that you all like this deck as it is super fun to play and can make easy comebacks.  I look forward to seeing what others will say.