I really wish there would be an emiter that you see (like a window or photoraphers lamp) and then the real emiter (invisible to scene  , and scalable in reflection node. Big emiters make huge inaccurate reflections) that actually produced the light . It would be nice if these two things could be the same... But we are not there yet.

By the time the emiter is big enough to stop making artifacts, it is washed out and lacking contrast.

 

You are right. There are anomolies from Zbrush as well. I see some of mine where polys are raised out in spline like fashion in precalc and later produce missreads and artifacts.

SR3 might fix some of ths.