I set QoS on that VSC to 'Disabled' .. no improvement
We're running firmware 5.5.3.0-01-10326
More details...
Controller: MSM765zl (Team of 2)
APs: MSM422 and E-MSM460
VSC Config...
Controller Authentication: YES
Controller Access Control: NO
VSC Ingress: SSID
Broadcast Filtering: YES (have tried 'NO')
Allow traffic between: 802.1X (have tried 'All')
QoS: Disabled (have tried 'Diffserv' and 'VSC Normal')
Mobility: NO
Fast Roaming: YES
Security Filters: NO
IP Filter: NO
MAC Filter: NO