I have been using a Balance 20 for about a month. It is running firmware 8.1.1s048 build 4990. I have two WANs, and one is configured with manually specified DNS:
Determining the DNS being used can be complicated. There are DNS settings in browsers, OSs and routers plus there is old and new DNS. A list of testers is here
If there are DNS settings in a browser, then different browsers on the same device can/will return different results.