Thank you for that screen shot. The way you have this set up now is that there is a primary Radius server, and several backups in case the primary Radius server goes down. But until the primary AP stops responding, all requests go to the primary AP only.
To set up more of a ‘load balancing’ situation, you’ll want to go in to XIQ> Configure> Network Policy> Open the network policy in use> Open the Radius SSID> In the Authentication Settings section of the SSID, below the Radius Server Group you have configured, there is a check box for the option to “Apply Radius server groups to devices via classification”. I would recommend using classification rules to determine which clients reach out to which Radius AP for authentication. This page goes in to more detail on the Radius Server Group settings.
Hope that helps!