Quick update.

I've posted the reflection glossiness study on Vray chas group forum. One of vray developers vlado joing the conversation. Interesting point he mention was that in case of vray the specular actually is a needed effect.

" However, mathematically, we do have two different methods to compute those reflections. One method is guided by the light sources and involves tracing shadow rays; the other method involves tracing reflection rays. The first method is traditionally referred to as specular higlihts. Both methods are correct and produce accurate results. (At the same time, neither of these methods is what actually happens in nature.) V-Ray combines both methods to get you the final result in an optimal way (in some situations speculars produce less noise, in others - reflections are better; V-Ray uses multiple importance sampling to combine them.) In fact, you won't get a correct result if you disable speculars - in that case part of the result will be missing."
Chaos Group - Vray forum render theory - http://www.chaosgroup.com/forums/vbulletin/showthread.php?68345-Understanding-of-glosiness-and-accuracy-in-materials