After ~400 crafts, no duplicate has been made yet. Either I'm 1 out of over 300,000, or this exploit does not work. Do not attempt.
Test logs:
Code:
EDIT 1:
Grabbed the mats, and started crafting with a nobles card. With 32 possible outcomes, I have roughly a 3% chance of getting a duplicate. Letting a bot spam craft while I wait and see.
EDIT 2: Mathematically speaking, after 143 tries, I should have a 99% chance of getting my card. Will craft for 10 minutes or so (> 143 crafts) and update.
EDIT 3: Nearing the 5 minute mark now, which puts me past 80% chance of getting my card. Noticed that the recipe actually crafts a different item.
Darkmoon Card of the North - Item - World of Warcraft
It's possible that this item transforms into one of the 32 choices as it is created. However, that means it won't be able to stack with any card, disproving this exploit.
Will continue testing.