I created a thread you can view by Clicking Here regarding this particular issue on the Bug Report Forum.
It appears that if you have a specific amount of Hearthstone Wild Card’s, That this can cause you to not receive any loot. If you delete the cards, You will receive loot as intended. At least that is how it worked for me!
You don’t really need those cards in your inventory anywho. As you only use those for the 1-time quest.