So far, I've found that Simulacrum will hold for a very long time if the mob isn't taking damage.
Once I start nuking, it breaks the illusion very quickly. I've actually tried to mind wipe my target to make the illusion last longer, because I
think it has a lot to do with hate, and one time it actually worked. However, it only prolonged my clones distraction for only 1 second, and then the mob broke it for good.
I use it a lot for crowd control, when we pull too many. For soloing I typically DOT and kite my way to victory.
