As much as i enjoy playing missions and having fun with friends I have to say this game's mission rewards are terrible. With only being able to farm for gold and faction points the game becomes boring and stale quick. I would like to suggest a rework that would allow players to receive rewards that are worth the effort.
Let's start with changing how the card system works. We can make faction cards drop from missions from those said factions and no longer requiring to shuffle with points. For example Hades faction cards can only drop from A low blow, in media res or double agent, etc missions. Also since this new system would essentially make faction points worthless you could add in a card upgrade system, where you would be able to spend faction points to upgrade cards and make them stronger. This could open up a lot of features for the future. Though the cards would need to be adjusted so that they don't break the game with insane stats. Also character specific cards would work the same way except they will drop depending on what character they take on the mission.
Well this is all I can suggest at the moment, I hope the dev team can make use of this post as i feel it can improve this amazing game.