Vol 1, Book 6, Chapter 5

I seem to have hit a bug in a place I didn't expect: a Volume 1 epic quest. It's the one where you have to beat Sorcerer Tath at Tor Gailvin in Angmar... but I can't fight him! He's just sitting, working his mojo while his ghost buddy floats in front of him wielding purple lightsabers. I ran up to them expecting aggro but nothing happens. Is there a step to this I'm forgetting or what? :/

EDIT: I tried back today and was able to complete it. It seems the issue was Tath's duvardain buddies hadn't respawned and they're what trigger his aggro. Must have a long spawn timer though...