I never liked the idea of classes. It forces you to make a choice and you can't even change your "class" without paying money (and it doesn't make much sense to be change it for free whenever you want either), and sometimes you can't even change your "class" and are forced to start over when you realize the class you selected is weaker than others. Freedom is better.
you should introduce an auction house or some form of player market one to increase selling value of cards, two to add an economy, three if it is unlocked by level then something to look forward to and finally something to do and think of deck combinations while waiting for something...
I never liked the idea of classes. It forces you to make a choice and you can't even change your "class" without paying money (and it doesn't make much sense to be change it for free whenever you want either), and sometimes you can't even change your "class" and are forced to start over when you realize the class you selected is weaker than others. Freedom is better.