Funny, not rebuilding your entire deck between acts is one of the things I like. I like the idea that you can't tailor your deck to each act individually. But I guess it's what you get a buzz from!
Same for me. It goes so much smoother to use the same deck every time.
Now I'm wondering if there are cards that force you to "downgrade" your deck. Say, you get scared stupid by Cthulhu and your skills suffer because of that and you have to replace say x amount of XP worth of cards with lvl 0 cards.
If not, there should be. Or maybe like adaptable - downgrade so many cards to reclaim/redistribute the experience.