Even just giving a random golden epic at the end of every wing on top of what we already get would have likely been enough to get me to buy them.
If they think I will pay a premium to get access to extra single player content, they are mistaken.
To be honest, I don't understand this mentality. Golden cards in general are useless bling, and a random golden epic is unplayable useless bling. You'll pay for that and not for hours of high-quality PvE content? I mean, Hearthstone PvE is better than many standalone singleplayer games.
It's a combination of lack of willingness to invest the time and already having very similar single player formats in Hearthstone as well as having other games I'd rather play. Even having the first chapter of the new adventures for free helps a lot. If I was very actively playing Hearthstone I would be more excited for the adventures, but I'm not.
About the Golden epic (and its dust), it's not an either-or. I would not pay (whether by gold or real money) for a golden epic alone, but bundled to sweeten the deal of the adventure, sure.
Oh but uh, I might have missed the detail about the golden pack at the end. The last adventure had as a final reward that cloak legendary that I didn't want. I'll look into the details of this one again and reconsider.
The preorder is different. You always get a relatively good deal off of that, and my reasons for not pre-ordering are simply not feeling the need to spend that money given the amount I play Hearthstone right now. I've preordered in the past.
Edit: oh you mean preorder the adventure? Oh, I dunno, I had too much going on in my life to pay attention.