If yu have ever played any other online game, you should probably know by now how things work when the devs add smth new. For example in League of Legends every time they add a new champion, it's op and insta-ban every game, but it gets nerfed in the next patch so much that it barely sees play. It was literally the same with Galakrond Shaman last year. Right now we can probably expect a "death patch" for DH incoming.
The demon hunter is 100% broken. I have been playing at diamond 1-3 levels (Aggro Hunter and now tried heal Priest) and I only face Demon Hunter. With the massive draw (Skull of Gul'dan especially), the healing with life-steal and totally OP cards (like priestess of fury) this is no longer fun. I don't think they properly tested DH. My guess is that Skull of Gul'dan and Priestess of Fury (among others) will be nerfed within couple of days.
The deck with 76% winrate has the smallest playrate of the other decks. DH is currently overrepresented in general, so while it's definitely performing adequately, it's not known where it stacks up yet.
I'm just astonished at how incomepetent the developer team is. From the very first reveal EVERYONE AND THEIR MOTHERS knew that DH will be op and that literally 70% of the cards need a nerf. But yeah. Let's ruin Day 1 through 7.