While playing in custom games or even just sitting in the main menu I will randomly disconnect from battle.net, having looked into this issue from other posts it seems you guys keep asking for a WinMTR so i will try to link my own so you can look at it and try to figure out what is causing this issue.
While writing this I have Warcraft 3 running in the background with the test running so that way I can post it along with this post so it is as current as possible at the time of writting this
|------------------------------------------------------------------------------------------|
| WinMTR statistics |
| Host - % | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
| RBR50.attlocal .net - 3 | 175 | 170 | 1 | 118 | 4085 | 9 |
|____________|||||||
Hey there South,
Thank you for reaching out with that WinMTR test data. While the MTR test is only showing one hop (this typically happens if you use your own IP as the “Host”), the issue is quite clear:
| RBR50.attlocal .net - 3 
| 175 | 170 | 1 | 118 | 4085 | 9 |
This first hop is the connection from your computer to router or modem–depending on which device you’re connecting to–and the test is showing 3% packet loss as well as ping spikes up to 4085ms.
If you’re using WiFi, the easiest way to see if your WiFi devices are the problem is connecting directly to your modem or router via Ethernet. Note that we do not directly support wireless connections. If you find that WiFi is the problem, you can contact the support team for the WiFi device or the wireless router.
If you continue to experience issues, ultimately this would be an issue to bring up to your ISP as they may need to run some diagnostic tests on your modem or router and/or temporarily replace the device to determine what is causing the packet loss and latency on that hop. Keep in mind that you can request to speak with a “level 2 or level 3 technician” when contacting the ISP, as the front-line representatives typically only have access to basic diagnostics and troubleshooting tools.
I hope this information helps get things fixed up so you can get back to playing as normal!