My get-tagassignment and new-tagassignment commands takes 11 seconds on my 5.5 production vcenter with 1200 vm's. My beta 6.0 cluster is basically empty but it returns in just a second or two.
I can do it from the web client in just a couple of seconds.
Start with ds.log? I see lot's of Processing unresolved entities messages but haven't identifies what that means yet.
PS C:\Users\edsilber-8570> measure-command {Get-TagAssignment -Entity eric-vm.oit.ncsu.edu}
Days : 0
Hours : 0
Minutes : 0
Seconds : 12
Milliseconds : 394
Ticks : 123948443
TotalDays : 0.000143458846064815
TotalHours : 0.00344301230555556
TotalMinutes : 0.206580738333333
TotalSeconds : 12.3948443
TotalMilliseconds : 12394.8443
PS C:\Users\edsilber-8570> measure-command {New-TagAssignment -tag notprotected -Entity eric-vm.oit.ncsu.edu}
Days : 0
Hours : 0
Minutes : 0
Seconds : 14
Milliseconds : 497
Ticks : 144975026
TotalDays : 0.000167795168981481
TotalHours : 0.00402708405555556
TotalMinutes : 0.241625043333333
TotalSeconds : 14.4975026
TotalMilliseconds : 14497.5026