That MTR of yours does not look kosher, 18ms average to your router via cable? 4% packet loss to Blizzard which looks to be originating between your router and the Vuma gateway. I know they have limited icmp in some cases, but not to that extent imo. This is less about optimal routes and more about loss on your line it seems.
I'm not on that SACS route anymore and only have that one screenie of an MTR. When I plugged direct into CPE we switched to comparing using the LookingGlass tool.
When I was plugged into the CPE direct, I had the same in game experience as default setup, and when switched to the London route, I had the same new experience when direct to CPE or via router.
Unfortunately it's hard to control the tests when unable to easily switch through the testing variable, but up until then I tried to keep it as standardised as possible.
As Example, before even making noise, or while doing it, I have the ability to provide 1x PC, Win10, 2 diff LAN ports, 1xLaptop, Win10, LAN to router, wifi to rouuter, LAN to CPE, 1x MacBook, wifi only, MacOS and Mac version of WoW.
I figure for the most part if I get similar experience with that variety of hardware, software OS, software App and networking, it goes a big way to excluding variable on my end.
That being said though, crazy **** still happens