I said I was ruling out the 5500 as the issue. The router did not change the results at all, it was equally up and done with or without the router.
I think everyone in the neighborhood is home browsing, streaming, gaming, etc. I will run some tests later when more people are asleep. I think the bandwidth is there now when I need it, as I do not have any issues streaming multiple HD movies. A speed test to the Time Warner internal server is consistently 30+ down and 5+ up, even right now. I doubt they would consider it an issue.
Also of note, since you mentioned dlink said they have no NAT problems with the default settings, I decided to stop port forwarding as I never needed to do that with the 360 with either of my dgl routers. 3 reboots of the XB1 and it was open every time, no port forwarding needed. I think forwarding the ports was a reaction to the bug where the XB1 comes out of sleep (instant on) and the NAT ends up strict. I will try just rebooting the XB1 next time that happens and see if it works better without the port forwarding.