Everyone seems to agree this game is frightfully difficult with one deck and not too hard at all with 4 decks in play. Just the amount of resources available and your choice of tactical options makes things much easier. I propose the following scaling fix. The Staging area receives 1.5 cards in the quest phase (rounded down)
So this would translate as
1 Player = 1 Card
2 Players = 3 Cards
3 Players = 4 Cards
4 Players = 6 Cards
I will play-test this soon, but would love to hear some feedback.