Well, I lost every game against it, to begin with xd while racking up >80% winrates on 2 different decks at the same time (samples 65 and 37 games respectively, but ended up around 75%)
That’s quite a tell, wouldn’t you say?
Naturally, it’s possible the deck simply counters both of mine, but even if that’s the case, shouldn’t the difference in winrates be a bit lower?
Every scenario assumed leads to it being overpowered.
EDIT: You asked, I delivered xD Now, this would be far from the first time that I rush with my conclusions and end up taking them back, and I’m sure you could find exceptions to disprove my thesis, and you’re quite right.
It’s just that it doesn’t happen quite as often as me being right. Fringe scenarios are needed, like a combination of luck (low sample) and the learning curve. Those are my first 10 or so matches against a new deck, so it’s reasonable to conclude I am yet to learn how to face it, and the sample is just too low.
But hey. The fact I’m aware of all of this should tell you enough 
I’m aware of many more things than your average guy
EDIT 2: This might be a good time to take ALL of this back, because Quest shaman lies in the top 3 worst decks in top 1k.
So I take it all back, thanks for sticking to the end 
Oh God, I just love being wrong, don’t I
But hey, if I was lucky, I wouldn’t have to be this smart, so I guess this is just another proof that I’m generally on point 
win-win!