After leaving the oasis area I was intercepted by a planetar and his cronies. Killed the lot of them looted their bodies but no portal appears. I didn't think anything else of this and went on to complete hexxats quest. I'm up to abizgails lair now and still dorms quest has not triggered.
After doing a bit of reading it seems dorns quest is supposed to trigger after that encounter.
So I loaded up a save I had just before the sacking of saradush killed yaga shura again went to the oasis and traveled backwards and forwards until the interception area appeared. Except this time no planetar no cronies nothing.
Seems like some persistent variable has been set the upshot is no dorm quest.
Incidentally upon loading my later save back up it can travel to and forth between locations and eventually appear in the interception area where I had killed the planetars and his cronies but no portal no nothing.
I'm on the latest version of the ipad with all optional content installed. Posting a saves game is a possibility but I would need to get I fun box