Not sure how well ^^^ works, but when I run it we have everybody stack together about 3/4 of the way down the steps so that the hostages are neatly packed.
[Image: http://puu.sh/6eLtv.png]
Everybody in the party moves together at the same time while stacked, and almost never come across mass spawn. Just need to be quick about running back to hostages when mobs spawn and puppet/AoE pet mobs to make sure they don't scatter.