I ran into the same problem on the quest "A guild without a master". I entered into the tower. A cinematic with alliance soldiers started. After that, I killed them, went on the top of the tower, met the guild master and accepted his quest (aim was to help them to go out of the tower). Some alliance soldiers popped, I killed them, and after that : nothing...

I'm not able to speak to the guild master and the 3 doors of the tower are locked so I'm totally blocked.

I made a search on the forum about this issue but I didn't found any post talking about it.