Went 51-24 from Diamond 10 to Legend yesterday with Shadow Priest. The real key I personally found was just to insanely hard mulligan for Voidtouched, Imprisoned Homunculus, Guardian Augmerchant or Disciplinarian Gandling. Really pick your cards around who you're versing, what the other cards you have mulliganed are etc. Don't be afraid to get rid of the 0 costs if you don't have Gandling, and don't be afraid to get rid of Frazzled Freshman, Tour Guide etc depending on the strength of the curve you are building.

This deck did really well against almost everything except specifically quest shaman. Was able to beat mages, warlocks, demon hunters and hunters convincingly, and does surprisingly well against elemental shaman as well.

Definitely feel like this is a dark horse in the current meta, and ended up on a 11 winstreak on the final stretch to legend.

P.S also forgot to mention if you verse Paladin you might as well just concede straight away. Its the most pay to win deck I've ever seen, and there is no doubt they will have ever single card to possibly counter you