i believe that these mobs in fact do not see invis. While making the run to the AiW area today i got hijacked and smashed by these guys but they were around a wickid performer in the upper parts of the theatre area. When i went back to kill the see invis mob in the way i realized that The wickid performer, being a named mob most liekly saw thu the invis and jumped me, well i believe that is what happened to me today. the reason for this is that there was more then one impish performer up and they did not drop anything of note. Also something to be aware of is when pulling mobs form the terraces from the theatre pay close attention for aggro messages it is possible to pull everything below by the stage and stuff and have one hell of train on you ina hurry.