Forewarned is forearmed bug 
after kill undead scout
and don’t get reward and can’t pass quest
My Char was Guardian Human Vigil
Forewarned is forearmed bug undead scout
I had this happen to me as well. I reloaded the quest and did it a second time. It worked. The Dec 3rd patch notes also made note of this as well. Hopefully it is fixed for good.
Well, as of December 31, I still can’t complete it. Just ran it twice and both times bugged out after killing the undead scout. Corpse despawned, but no cut scene, so I can’t complete.
Level 53 Human Warrior
This is still an issue for me. I fight the orrian scout and the cutscene plays. Forgal tells me to meet him at Claw Island and swims upwards through the ceiling.
I’m unable to complete this quest. I have attempted it 5 times now.
I have tried swimming with Forgal and not getting in front, I have made sure that he is not in combat when I trigger the cutscene all to no avail