slow RnD Multiscatter parsing with millions of instances

very slow multiscatter parsing with many instances comparing to vray / 2-3 times slower
i tested scene with 5000 000 grass instances. 25 sec corona waits for something and does nothing, parsing starts at 28 sec.
it takes 40-50 seconds to start rendering in corona. comparing to corona scatter - it takes 10 seconds. vray starts rendering after 20-25 seconds.

is there a way to speed up parsing using multiscatter? or it could be improved in future corona versions?

corona 1.5 multiscatter 1.3.6.3 3ds max 2016, 2014

already posted to mantis, closing it down here - please do not duplicate threads between mantis and forum