Someone else has experienced the same issue with a download going at less than 100 KB/s, I have bad internet personally, but they had fiber and were experiencing the same issue as I was a moment ago. IDK why but it keeps dropping below 50 KB/s, even when I relaunch battle.net and force the update agent to close through task manager. Even when I use my hotspot which has a considerably higher speed than my home internet its still downloading at a very slow pace. Looking at my task manager ethernet panel shows it spiking and dipping sporadically like as if the connection is bad.
Anyone else experiencing this issue, not sure what to do at this point other than sit for an hour or two as it slowly downloads.
UPDATE: seeing as someone liked this post recently, I figured out my issue was with nvidia GEforce, in that as soon as I started to download the new driver update my WoW update began to work fine. Someone mentioned uninstalling geforce solved their issue, for me the above is what fixed it, so mess with your geforce if you have it and see if it solves the issue for you!