Hearthpwn

Hey, I did the same thing as you: I was struggling to find the best control deck to climb then Clark’s deck made me realize how undying allies and balaseth can be powerful in quest priest.

since I included them I’ve never lost to DK or aggro priest, and that’s a large majority of the games I played! Demon hunter seems impossible to beat, though.

your build is cool but I think Svalna and harvester are too slow. In which matchups do you feel you need them ?
 The weakness of my deck is having only one 7 drop and one 8 drop, just like you, but also no way to get another because I have no steal/copy/discover cards. It’s not such a big deal because the quest is only for blood dk - you need to play around the disrupt cards and you win.

As you mentioned, The Harvester and Svalna can make the deck too slow, so they can be replaced with other cards that can counter the most common classes you'll face at the time. 

• The Harvester - I really enjoy stealing my opponent's original cards and seeing their surprise 😂. My favorite cards to target include Astalor (2/5), Brann (3), Guff (5), Shadowstep (0), Reconnaissance (2), Identity Theft (3), Bound Soul (0-1), Lady S'theno (3), Stewart (3), Legendary Invitation (2).
• Svalna - I often use her in matchups where I need more control than my opponent, or when I need cards like Drown to remove deathrattle minions that benefit them in the long term, such as Aegwynn. I also use cards like Cannibalize/Void Shard to heal in some matchups, like Quest Warrior, and Identity Thief/Animated Dead to combo with The Harvester.

Demon Hunter is not my favorite matchup either, and whenever I add 2x Streamcleaner, the RNG gods never seem to pair me with them. If they do, it's with a Demon Hunter that doesn't use Souleater's Scythe card in their deck.

I frequently use the Quest card just to discover my deck 2 times and put pressure on my opponent to rush to end me quickly or make them hold onto their steal cards in their hand, waiting for me to complete it and steal it with The Harvester if I can (e.g. Theotar/Identity Thief)