A new expansion always put new blood in a old card game, even if the luster doesn't always last for long.
It doesn't help the last Gwent patch made my favorite deck (Scoiat'el dwarves) weaker while also buffing a card I hate (Yennefer Conjurer) by making her immune to Yoverth (which I crafted solely to shoot her right in the face)
I could perhaps make a new deck but I lack the new meta cards and after riding a OP deck for so long, going with a weaker one just isn't the same.
It's not say Hearthstone doesn't have it's share of problems. The new Quests seen to be really powerful, and powerful in Hearthstone translate in mandatory while making some decks kind cookie-cutter like the Jade ones.
But it's just 2 days into the expansion, maybe the meta will change, or maybe Blizzard will not wait 6 months to make changes if a deck is dominating the season.
For now, enjoy your quests and exploring Un'Goro.
For now...