Windows started paging 3dsmax's commits. As you see, Disk 1 shows 100% usage.
That explains low CPU usage, as the occurring paging will be limited to the HDD speed. This also cripples all rendering performance.
7mio instances with 200,000 mio polys is quite a thing. Embree can crunch through any number of geometry, but it does it in a more memory intensive way, I'm not familiar with the details though. Generally the idea of instances is to lower memory usage, but embree is more naive and this is one of the places where intel's render kernel gets it's speed from. What you could try to do is to merge many similar geo's into one object. It improved memory usage in the past for me, although I have not worked with such heavy scenes in corona. I get the feeling though, that god damn 200000mio polys won't fit 16gb anyhow, you are definitely low on memory.
So it kinda goes back to the good old ideas from me: decimate the instanced object's polys, turn off displacements if any and
get more Ram.Also there is this
very old article for Vray it's not much help but maybe will give you a good idea and is a fun read, while waiting for some official say and tips.
any body there?
Generally speaking you are using a daily, so expect to hit some walls here or there, devs are sweating to fix stuff, 24/7 text support has to be sacrificed for that.
Corona does not support out of core rendering, so bucket mode does not lower ram usage and did not when you had 1.3 installed.