This deck isnt just OTK you can win by a lot of ways, but mainly its OTK.
You want to focus on surviving and controling board with your clear spells such as Excavated Evil, Dragonfire Potion, in the mean time draw as much as you can, but dont overdraw Northshire Cleric, Loot Hoarder and more.
For the OTK combo, you always need buff from Justicar Trueheart and Raza the Chained after that you play Auctionmaster Beardo and Embrace the Shadow, now it depends on opponent health..if he is up to 30 you need to have Holy Smite, Mind Blast and Flash Heal + some low mana spell = 32DMG. It depend a lot on situation.
Sometimes you dont even need buff from Justicar Trueheart, but you can deal so much more damage than 32, but you use those other spells during the game.
Kazakus it really depens on situation, but most time you take make spells for clearing board 5mana spell for turn five, 10mana spell for late game, 1mana spell for combo with Auctionmaster Beardo
"Kabal Courier ---- When you get Coldarra Drake take it..:D
Northshire Cleric, Loot Hoarder,Acolyte of Pain,Power Word: Shield ,Kabal Talonpriest
Against aggro deck you can keep AOE.
Possible switch : Garrison Commander for Gnomish Inventor
Keep in mind that this deck is really hard to play and requires a lot of decisions in every game.
You can ask questions in the comments.
Here is link to orriginal deck :
I did some adjustments, because i think that in the original deck you miss aoes and you have cards what you dont need.
Coldarra Drake OTK.
So far rank 11 using only this deck
How to cancel cancer : Pirates everywhere