I have an improvement!! (which is something I've not been able to say since I first encountered this issue)
I don't have a lot of time, so here's the TL;DR version.
Try setting the 3D settings on the video card for the master image to:
In my environment that brought a login that was 5 minutes 35 seconds down to 50 seconds. I know 50 seconds still stinks, but it's better than nearly 6 minutes!!
Right now login for "Window - Large" is 40 seconds, and login for 2x 2K monitors and a laptop screen is 50 seconds.
Are you using GPU's?
Right now the two Nutanix clusters I'm using for this round of testing don't have any GPU's. Now, with that being said I have some C240's packed with T4's that will be coming up next week, I'll test and report back my results as soon as I can.
In the meantime I've got an older 7.1 environment with K2's and M60's that I'll experiment on today.
Also, ATM I've only experimented with 2GB's of memory, I'm going to start bringing that down to see if there's a point where performances starts to suffer again.
Is there anymore information regarding this issue? We are currently experiencing the same issues since upgrading our vm's to Windows 10 1903. Issue does not occur in Windows 1803 or 1809. New gold image does not resolve the issue.
Without 3D rendering enabled, using multiple monitors, virtual desktop takes anywhere from 4-5 minutes to launch. With 3D rendering enabled desktop takes 90 seconds. (This is actually decent in our environment). Desktops seem to have high CPU utilization in task manager during login coming from DWM.exe when 3D rendering is not enabled. When 3D rendering is enabled DWM.exe does not spike CPU at all.
Versions are as follows.
VSphere - 6.7 U3
Horizon - 7.10
App Volumes 2.18
VMWare Tools 10.3.10