Unfortunately Descent of Dragons was a total mess on release. Shaman got blatantly outrageous stuff and it has resulted in one of the least balanced metas I've ever seen. Only two classes have above 50% winrate:
Priest at 36.6 is ****ing hilarious, that's maybe the worst class winrate in the history of the standard format. Luckily Blizzard already came out and announced on Reddit that nerfs are planned for next week, however it's very disappointing that they ****ed up so bad and ruined the first few days of the expansion which are usually the most fun time to be a Hearthstone fan