We've heard from several of our players who found that they had not been receiving any Steam trading cards, despite having bought DLC for EC.
After a bit of investigation, we managed to trace this error to in-game microtransaction purchases being the only purchases counting towards the accrual of Steam trading cards; Steam Store DLC, on the other hand, was not being considered. We've raised this concern with Valve directly, and they promptly resolved the issue.
As of now, all EC DLC priced over $9 will drop trading cards as well! Players who have purchased such content will now begin receiving these cards for their hours in game.