There are documented issues in routing with third and fourth parties that need to be addressed to facilitate better diagnosing at SE's end. Need to attack this from both endpoints, as either your ISP or SE's ISP (or both) may be the one with the agreements to use these other ISP's as routing partners.

open resmon or run netstat to find the IP your client connects to while in game... it should start with 199.

Run tracert, pathping, or similar report tool to that IP, copy/paste the results into your bug reports to both your ISP and SE so they can investigate any potential issues in route, and hopefully get the responsible parties to clean up their shoddy service. Then maybe SE can better pinpoint issues that may need addressing on their end.