I'm currently experiencing this same problem although perhaps slightly different, running
6.3.1.2 as well.
I have noticed that regardless of entering system settings on the controller to send all radius packets from a specific VLAN, or as cjoseph suggested setting the nas-ip parameter. All Airgroup radius packets are coming from the incorrect VRRP address.
I also stumbled upon this because only one of the VRRP addresses had been setup in our clearpass radius server.
Currently the controllers have two vrrp addresses a 10.16.x.x for corporate and a 192.168.x.x for guest/dmz. For some strange reason the corporate clients (10.16.x.x) requests are coming from the 192.168.x.x address and I can't seem to change it.
Did you have any luck with raising a case mzac?
Thanks for the help.
-Liam