To date, every Adventure Pack has included 8-10 (usually 9) new player cards, plus a new hero. As the game grows, the number of possible decks has exploded, to the point where the addition of just one new card sometimes opens up a new deck archetype, usually with multiple variations (e.g., Strider, Sword-Thain, Elven Light, Gather Information). And nearly every hero opens up a new deck archetype.
I would almost rather see just a few player cards published each cycle (say, 8 in a deluxe and 2 in each adventure pack), especially if those player cards that did get published were of the calibre of the examples I gave above. The adventure packs themselves might start to include two quests instead of just one, or to include encounter card setups that make use of the larger number of cards. Heck, maybe they'd start to publish the nightmare decks simultaneously and include them in the adventure pack!
I'm not even sure this change would decrease sales of the game - I enjoy playing the new quests, especially because I'm interested in seeing what new ways the designers have come up with to challenge us or to smash powerful deck archetypes. And, if the player cards were as game-changing as some of the examples I gave above, I certainly wouldn't mind. As it is, only about half of the player cards that I get these days actually make it into decks. Partly this is because of a lack of time on my part, and partly because some of the player cards are very conditional and require careful deck-building (Master Ironsmith, Guarded Ceaselessly, Arrows from the Trees, Scouting Party).
But I digress. My original query was: would you balk if FFG published fewer player cards?