4 resources is a lot to spend on something that does no damage. As an X-wing player I'll tell you the best defense is a good offense. With JUST Vader and a single cheap upgrade on Jabba, I hit for 5 damage a round. I don't care about stopping your Prized Possession and if anything I see it as a win that resources were spent on it. Vader will have other dice (via upgrades) and Jabba will continue to insure the best results. It's a smash mouth deck.
Does it beat everything? Probably not. I'd hope the game is more balanced than that. I see 3 and 4 character decks giving this duo the most problems.
Still... 5+ damage a round consistently.. =)