Just got my new R7000 installed today and for the time being I'm using the stock firmware.
One thing I noticed that doesn't work is dynamic DNS with the Opendns.org service. It will use their name servers of course, but the router won't log into their site / service, therefore the stats don't get collected. I also cannot use any dynamic dns other than the three in the pull down menu.
Is there a workaround?
I don't know about the capabilities of the stock firmware, but I use XWRT-Vortex and DNS-O-Matic (run by OpenDNS) to get set up. If the stock firmware supports it, this might solve your issue.
Good luck