I have seen several mobs, mainly in missions, appearing to walk floating above the ground. While I've generaly been dismissing it as a visual bug, last nite while me and my wife were playing, we killed one of these "air walking" mobs, and were denyed the xp and percentage towards our mission token from this mob.
This was a building type mission so there were none of the rooms with the green goop (don't get me started on those !!!)
