Mesmer party target
Since the clones are supposed to be identical to the Mesmer, maybe they should get the target showing on them also.
Actually when you call target on a mesmer you get unmarked when you cast an illusion and they have to mark you again.
If you create illusions with dodge roll, the mark remains. I am not entirely sure about mirror images, but I guess it also remains. The only time the mark dissappers is when mesmer goes invisible (just like mark on thief). But that also isn’t a big issue, because it’s very easy to find the real one and mark him anew.