Over the last few months I've experienced the same bugs on this trial as others have posted here and across the internet. I was able to complete the event just a few minutes ago, so either it was fixed, or a fluke, or the strategy I used this time worked to avoid the bugs. In any case, I'm posting my experiences in case it can help anyone else.
I did the event with me (85 ranger), my box (85 cleric), and cleric merc. Long, long ago I was present on this event when it was a raid, and I remember how the mobs in each room would be kited as the raid would kill one mob at a time. Since the reports on the bug often mention that the person killed all the mobs very fast, I decided to try to reproduce the old raid method in case that would help.
I stayed by Alekson Garn, had no one in the second room, and my cleric with merc in center of the third room. I hailed Alekson Garn, /say ready, and began the event by killing the mob Alekson Garn turns into. The madmen npcs spawned in all 3 rooms, along with 1 girl in the second room and 1 girl in the third. The npcs in room 1 (Alekson Garn's room) charged me, and the madmen in room 3 charged the cleric, but all the npcs (including the girl) in room 2 stood still. I killed a couple of the madmen in his room and then dragged them to room 2, in case they'd kill the girl. Once there they agroed me, and I turned and I killed the madmen I dragged from room 1. Moments later the named from room 1 spawned, so I ran back and dragged him to room 2 too, and killed him. I then killed the madmen of room 2 and another named spawned. I killed him too. Then I ran to the room with the cleric and killed those mobs to spawn the final named. I killed him, then all the girls despawned and Alekson Garn respawned. I ran the cleric over to him and hailed:
You say, 'Hail, Alekson Garn'
An ethereal mist descends from the air and surrounds your very being. Your body begins to emanate with the power of Alekson Garn.
All these mobs are headshottable though I was careful not to kill them all Too fast in case that caused problems, and was sure to kill them in the order of madmen, named, madmen, named, madmen, named.

