What determines where Duty Roulette puts you?

[KisaiTenshi]

So I just did a leveling roulette, right. And here was the party:

Level 57 SMN (Me)
Level 70 SCH
Level 68 BLM
Level 35 DRK

and we got put in Sastasha. There was no logical reason for any of us to go into that dungeon specifically, so why that one? Why not the highest that we could all do (which in this case would be Qarn or Brayflox)?

There are two things in play. The content cleared, and the ilevel of the player.

It's entirely possible that any of those characters paid for a jump pot, and didn't actually clear the dungeon content. They might have leveled off PotD, and thus are only now playing it.

But the more likely answer is that someone doesn't have the correct gear, so you got dropped into a dungeon that their ilevel can complete. Usually when you get dropped into the first three dungeons (Satasha, Tam Tara, CopperBell Mines) it's because someone in the party hasn't cleared it for MSQ. When that's not the case, it's because their ilevel (due to no right-hand gear) is around 15.

The remaining option is that someone specifically queued for it. ARR specifically doesn't look at ilevel, only the character level, as all 2.0 leveling content can be cleared without even the relic gear.