I found this tool designed by somebody who works for VMWare (I believe) and as the title suggests shows various stats/diagnostics from VMWare PCoIP sessions,
Overview of the tool: https://www.youtube.com/watch?v=F2OAdriDCms
Author's Website: http://mindfluxinc.net
One thing I found noteworthy is the log viewer has a category called "PCoIP Encoder Stats - Changed Pixels" which could prove useful.
I don't know if VMWare offers PCoIP in the free version (or if there is a free version?), however this could potentially be used to demonstrate and measure pixel differences between good/bad devices.
Perhaps the more tech-savvy of us here like @JTL etc will have a more informed opinion of the above, but it looks like it could be worth investigating further.