This was by design everywhere earlier on and required you to go to a sanctuary upon joining the group and returning to the area to see other party members. I had to go to Org and back to see members I grouped with in the Maw intro scenario. There was a huge outcry about it and it was removed everywhere but the max-level Maw it seems. So if you go to Oribos and back, you should be phase with other members as annoying as it is. I’m glad this design was mostly removed, but maybe they will consider it for this zone as well.
https://us.forums.blizzard.com/en/wow/t/grouping-in-the-shadowlands/736070