I know this post is a bit old but thought I'd give it a shot.   I'm having really bad logon times.   As much as 4 minutes plus for some users. Seems as though logon times don't get really bad until many users are attempting to logon simultaneously.   In an attempt to troubleshoot, I have stripped a user down to the bare minimum to create a base line.   This user has no apps assigned via app volumes, Less the 2mb of configs in UEM and no other user GPOs assingned.   upon logon, I see this:

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] ****************** Session Summary (User: ISBESPR1\jsled, Session: 1) *****************

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Logon Time: 43.66 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Logon Start To Hive Loaded Time: 15.80 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Logon Start To Classes Hive Loaded Time: 17.42 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Profile Sync Time: 0.00 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Windows Folder Redirection Apply Time: 0.00 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Shell Load Time: 15.72 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Total Logon Script Time: 0.00 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] User Policy Apply Time: 7 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Machine Policy Apply Time: 0 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Group Policy Software Install Time: 0.11 seconds

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] Free Disk Space Available To User: 19 GB

2020-01-09T14:57:27.001 INFO (1150-1834) [LogonMonitor::LogSummary] ***************************************************************************************

My question is why would my Start to Hive Load Time and Logon Start to Classes Hive Loaded Time be so high?    As I look at other posting in this thread, most are seeing around the 3-5 second range on both of these categories.    I have optimized using the VDI like a pro template and am on 1803.   Can anyone steer me in the right direction here?   Thanks