I played this mission today, 24/01/2015 and I got the same problem. The first 6 undead mobs have a buff that makes them invulnerable. Therefore Warmaster Efut get stuck fighting with first 2 unkillable mobs. I tried to move on towards the keep, and when I reach it, I automatically get to do second part of quest line, and after it all the other parts till the end. But after I completed “Report to General Soulkeeper” it keeps saying I have to complete Accompany Warmaster Efut. I tried to log out then in again, but I got to re-do all the Under Siege quest line. After reading some threads, included this one, I tried not to engage mobs before Efut did and everything worked fine. It was such a pain doing it all over again.