Trying to get the forsaken masters achievement

So the last kill I need to get the achievement is Aul. I was wondering if I join someone else's party and they kill an Aul do I still get completion credit?

Just curious because I'm terrible at delving and luck is usually not on my side

People offer a service called an 'Aul Taxi'. Basically, they have an uncompleted Aul node, and they invite you to join. You run from a completed node to the uncompleted Aul, you enter, and they leave the instance.

If the owner of the instance isn't in the zone when you kill Aul, you still get the achievement, but the Aul isn't completed, allowing the service provider to continue to offer the service.