I've found a couple of scenes like you describe, <name>. Always camps of humans and dwarves. Rumor among the caravans is a group of Horde marauders did it. Seems likely given the victims, and how brutal the attacks were.
Apparently the bandits fled Desolace once an Alliance marshal got hot on their trail.
If you're looking to track one of 'em down, I'd check Booty Bay. Ports always have shady characters coming and going. You might catch one trying to get a boat to somewhere.
