I camped this for quite a few hours over mutiple trips to the zone before I finally got Eslisar to spawn, luckily the aug dropped on first pop for me. I killed dozens of ph's where she finally did pop. I kept clearing north and south as well as Grelik/his ph and the mobs around him while waiting on re-pops. When Esilar spawned it was right where she was marked on my map. If you or a friend has headshot at the rank needed this is very easy to clear. On the plus side, Eslisar was never camped when I checked and nothing from zone in all the way to spawn point saw invis.