A few observations from playing this decks for a two hours now (8-1 winrate, only loss being poor draws vs a Rogue). Maybe I will update this post after I have played a large enough amount of games to add something statistics-wise.
1) It's super powerful, I have not encountered anything that feels better so far. Even though a lot of cards are underwhelming on their own, they have a specific purpose so tinkering around with the decklist is probably not a really good idea.
2) Your biggest problem is often not overdrawing and thus killing your winconditions. Hence I never played Weapons Project followed up by Harrison Jones. Both cards seem good enough to merit a spot in the deck though. I also often play Sweeping Strikes on opponents creatures just to make room for draws.
3) Da Undatakah is a definate keep versus Warrior for me. They run Hecklebot sometimes and there is no need to run the risk of them baiting out your Deathrattle King. Warrior matchup is as close to 100% winrate as can be.
2