Played this deck to legend from roughly Diamond Rank 4, went on a tear of 9 straight wins before getting stuck at Rank 1 for a while and losing to multiple final bosses. Finally hit it this morning. Came in at rank ~1500 legend so winrate must have been decent. 

Ideal curve is - Wailing Vapor into 2-drop, into Primal Dungeoneer, followed up with a very early Selfless Sidekick. Beats most decks on this curve alone. 

In mulligan always look for Wailing Vapor and  Primal Dungeoneer, if you expect a slow matchup I'd always keep the Selfless Sidekick. 

For Druid always keep and look for The Lurker Below, it wins so many token games.

Tech Cards - Acidic Swamp Ooze for Shaman and Warrior, and Death's Head Cultist for Hunter

For slow matchups, keep in mind that you can use Kazakus, Golem Shaper to get the 10-drop and corrupt your Carnival Clown.

I had a blast playing this deck and it took a lot of effort to learn all the lines and tune the deck properly, enjoy!