I know this is an old thread, but I just updated my 615 to the 3.13 NA firmware, and I'm having the same DNS issues. Unless I enter a DNS entry in on my devices, I can go nowhere. I have a static IP from Time Warner, and whether I use their DNS servers, or public DNS, I have the same problem.
This router has been working fine for ages, the only reason I upgraded was because I moved the office, and was just poking around trying to get everything up to date. Oops.
I'm surprised this is going on for two years and was never fixed. I downgraded to the 3.12 firmware, and everything works fine again.