I am currently on Diamond 3 and i have around 50% Winrate. It is not the best deck but hell it's FUN. If you are lucky and discount the potions you can even OTK with Mordresh. Don't have experience with Korrak and Mankrik yet you may want to swap them for anything else. Mass polymorph is a must agianst Priest and but agaisnt Priest and Paladin you may want to hold Potions until you play another guaranteed potion with Dawngrasp. 

Deck highlights i had with the deck:

1) Having a 7 dmg Hero Power with Dawngrasp

2) Building A LOT of snowmen 

3) OTKing a Priest with Mordresh by having 2 zero mana potions