I used my free Darkmoon Faire roll, and I got the Signature Questing Assistant. But I already had two regular copies of that card. I would have expected to be offered a reroll of those regular cards, similar to when I get a golden card from the Rewards Track. But that did not happen.
It doesn’t matter much. I already have all Common cards, so nothing lost. But it might be annoying for others, so I figured I’d report it anyway.