I can confirm Aurum Vale is definitely in leveling roulette, since I got it once about a week ago. IIRC, it is a completely optional dungeon, only required for progression of a couple of side quests like zodiac weapons and squadron rank so I'm sure a lot of people just skip it these days. There's probably a lot of players that don't even have it unlocked, which I imagine would impact the frequency of it being filled by the leveling roulette.