As much as I really like the Class Decks, it feels like they also create a disconnect from the scenario & storyline being played. Your hero finds an Ankh of Awesome in the game, but then needs to swap it out with a Spyglass from the Class Deck.
It's like Class Deck players are involved in playing a parallel game that aligns with the other Heroes that are playing from the box.
I understand the idea that a person can show up with their Class Deck and leave the game without affecting the card stock of whomever owns the Big Scenario Box. I'm not sure that having Class Decks is worth sacrificing the connection In-Game Characters develop as part of the world they're exploring.