The Horde aren't just here on a san'layn shuttling mission. There are lots of high-ranking Horde figures here. Something's going on.
One perk of dealing with important Horde targets is that they tend to be carrying important information. Look at this map I found on one of the bodies. See the big red circle around "Kings' Rest"? What is Kings' Rest? Why don't the Alliance know about this?
We'll have to look into it as soon as we get back on land.