Here’s what I would do if I could patch the game. I think it’s pretty good right now, but some decks hog the top of the power curve, a mini balance patch could alleviate that.
Along with a new game setting at the end, to ensure a self-healing meta and provide community-driven balance directions.
Comments welcome 
Nerfs
(credits to @deathsadvocate for Sunriser)
Buffs
New cards
New game setting: “Personal nerf”
Your account has a new setting. Choose ONE card you want to nerf: In any game against a human opponent, this card will cost 1 more and its cost cannot be reduced.
- You cannot change this setting during a game.
- You can only choose a card that is Rare or above rarity (no basic, common, or General).
- The two nerfed cards are announced on the mulligan screen before the game starts.
This post and ideas released under the Creative Commons CC0 license.

Though right now it almost seems like a better version of the original. Wonder if it needs a small adjustment.
Not sure if the can’t be reduced part is really necessary.