Do not go to crazy on the rarity of a card or trading or whatever… People will just use reditt of something and get their hand on the card… D3 has tried so many combinations of things and some work and some do not… They have tried real money AH, Gold AH, trade and now they are ingroup only trade because the others all failed. I do not think DB will be that complex and even though cards are rare after 100 hours almost every card should be unlocked or until SD makes new cards to create.
I would like to know how we obtain keys? Obviously we can buy more ad obviously key will be used to craft BUT how do you get keys without paying and what is the output level… Shouldnt we be testing that so we arent like this sucks or something?