There’s a common weapon that drops at the end of the Tomb of the Heretic, the new roguelike dungeon. I almost didn’t see it because of my item filters. Fortunately it stands out.
According to a reply by Zantai “It is indeed a bug and will be addressed in the upcoming hotfix”. I’m guessing that it’s not supposed to be common. I’m not sure what the range of values is, but here’s the reddit post if you want to compare.