Debugging Compiling speeds

I'm getting increasingly slow compilation speeds, and I'm losing my mind. I know the way to fix this is to split your code up into chunks, but I'd like to know exactly what is causing the slowdown. Note that I've already put all of my third party addons into the plugins folder.

Is there any sort of way to see what classes contribute the most towards compilation slowdowns? I'm honestly not sure exactly what slows down compiling in general, my only guess would be classes that interconnect to each other.

Also, is everything in the plugin folder considered to be it's own assembly definition? Or do I need to manually put assembly definitions in the plug in folder / editor folders to really take care of plug-ins?