I conducted some experiments on the game with all the classes and found a commonality. When you play with a certain deck for 3-4 consecutive games and win, your chances of winning drops significantly. This is not because of RNG; it is because the game decides your opponent, the cards you both draw and all the luck related issues. The tricky point is, the game doesn't do it randomly. It picks a side. That's why your C'Thun, Elise, Monkey, Worgen or whatever important card you will need are in the bottom of your deck most of the time. Another example is being unable to draw any aoe effect that will probably win you the game in a deck full of aoe spells?
I didn't find the right solution from the Internet.