I just ran Horn of Magnus and they were present for the majority of the map, from the very first enemy seen right up until the end event.
They at least seemed abscent from the end event.
Ungor Archers also waiting inside the cairn at the end. 
I just ran Horn of Magnus and they were present for the majority of the map, from the very first enemy seen right up until the end event.
They at least seemed abscent from the end event.
Ungor Archers also waiting inside the cairn at the end.