The connection test looks fine, all 438 packets are making it to Blizzard. However, your DxDiag is missing a lot of info from the top half of the report. From what I can see, you need to update Windows, and you’re using a Razer Chroma device, so it’s possible you’re being affected by this:
Otherwise, I would look at the power mode and make sure it’s set to high performance, or check for overheating. I have no idea if this is a laptop or PC due to the first part of the report missing.