I'd really like the ability to have some kind of idea as to what all is in my deck. Not a full-on "show every card available" thing, but maybe just the ability to see how many cards there are. Maybe give a breakdown of how many of each type there are, or even just give a pop-up whenever you learn a new skill that states how many cards related to that skill have been added into your deck.
It's always nice to see visible progress, and watching your deck slowly dwindle would be cool. At the same time, seeing your deck grow with new possibilities would be exciting! AND it would help reduce frustration from getting dealt hands you don't want if you can clearly see "oh hey, a good 80% of my deck is crap."