I think a large part of the problem with new players coming in isn't so much that they don't have all the cards, it's more so that there isn't really a safe place for them to play and feel like they have fair competition. The ranked ladder system is built more around climbing than about matching you up with similarly skilled opponents. Ranks 25-24 are relatively safe, but once you get towards rank 20 it's like getting thrown into a shark tank. It's really discouraging to be matched up against opponents that are swimming in legendaries when you haven't even gotten all of the basic class cards. Even play mode doesn't really create the best environment for new players. I really don't know what the solution is.