Right, we're really focusing on players building up their own collections and playing the game. If you have duplicates there's a crafting system, which allows you to break down (disenchant) what we call Expert cards and then use the subsequent Arcane Dust to craft new cards.
Expert cards are those you get from opening packs (packs are either won or purchased), or the ones you choose and get to keep if you win a game in The Forge. Basic cards are ones you earn just by playing a class, win or lose. Expert cards are denoted by a rarity jewel in the center of them. You can see both types in the screenshot here