To those who encounter the bugged Battle for Undercity quest

I've been phased out since Friday night and couldn't interact with Thrall to trigger the event. You can read more here: http://forum.warmane.com/showthread....85#post3124585

But I was fortunate enough to find a player who started the quest and it was working exceptionally great (mob spawns, fighting, dialogues, and most importantly, successful turn-in). I asked him what has he done to make things work, and told me that I needed to kill something at the Alliance entrance. I didn't get to ask him for more details though. I hope this helps anyone who ever encounters issues with this quest.