That is the main issue, if there is no way to make card values based on pack prices hold up at least 50%+ of their original cost, all earnings are just a complete fugazi and the willingness from players to buy packs or promo cards tanks which can be seen with the Zyriel card and Riftwatchers.
I have never been a pack buyer and always rather tried my luck on the secondary market picking up cards way cheaper. I did get a couple 100 packs for Chaos Legion though (from affiliate earnings) and I feel for everyone who got a lot more at the 4$ price.
It's going to be interesting to see how it all plays out the coming year.