I don't know if I was too unlucky or people just keep saying "first tried win". @@.
This deck doesn't work with me since I've failed thousand times before I replaced some cards from this deck then i got one-first-shot on his face.
Here is the deck i used to beat him:
I removed Sabotage and Assassinate because of theirs high mana-use, Pit Snake is also removed because of its ineffectiveness (the boss just one-hit on that snake everytime i put it on). I put some cheap Taunt minions and Kel'Thuzad to protect my 'face'. Combo Preparation + Vanish then put Taunt and Patient Assassin to regain the board control.
5