Tell you what, if you get the settings right, V-Ray can be pretty fast. I was getting long render times and I changed nothing but the camera exposure and now it’s rendering much faster. I placed a ball in my scene, made it almost pure white (200,200,200), and exposed the camera until it measures accurately. Just an interesting finding.
Scratch that! I also temporarily disabled displacement 
Interesting way to adjust exposure. Something I struggle on every scene. What part of the ball do you measure for correct exposure? The surface pointing straight at you, specular highlight, etc.?
I pick a spot that is pretty neutral; not in direct light, nor in complete shadow.