Warning: another complaining post.
During Brian Kibler's new video he mentions near the end that card number is an issue and I really think this is the core issue. Each expansion released only allows for gradual change. If the released expansion had significant card count there is a much greater chance we would see new decks with each release rather than gradual creep of current decks, which I think is the reason the game starts to feel so stale so quickly.
I wonder if we could get reasoning behind the current card count of expansions. Adventures seem to be artificially low just due to the number of bosses/class challenges.