I actually find the commons very useful; I'm 6 decks in and haven't found a card yet that looks completely unplayable. Compare a pack of Destiny to a pack of MTG and you'll appreciate just how playable Destiny's commons and uncommons are relative to it.
I was talking about that these cards are trash after second display as you have already each of them.
Nobody will trade uncommons against commons and so they are useless if you have already two of each common card!
Unless you have more than 1 deck.