In regards to VC failover time, this is taken from the VRD:
Once the election has concluded and an IAP is selected as Master it will begin broadcasting master beacons one a second to every slave in the cluster. These beacons are used as the primary failure detection mechanism since the Slaves will become aware that the Master IAP has failed if they cease to receive master beacons. If such an event occurs the Slaves in the cluster will continue to listen for a random interval of between 10 and 40 seconds. If they fail to receive a master beacon during the random interval then each slave will transition into the Potential Master state and will begin sending unicast beacon request messages to failed Master. If a the Slave does not receive a master beacon within 8 seconds after it begins unicasting the failed Master it will transition and assume to role of Master for the cluster.
When a Master IAP fails the clients that were associated to it will need to re-associate to a new IAP.
If Dynamic Remote Authentication Dial In User Service (RADIUS) Proxy (DRP) has been enabled and new clients attempt to associate to an IAP during the re-election process they will be required to wait until a Master has been elected
https://community.arubanetworks.com/aruba/attachments/aruba/Aruba-VRDs/76/2/Aruba_Instant_VRD_2016.pdf