It's probably not bandwidth, but a QoS issue. if you're using a fancy enough router, you can adjust it to prioritize QoS and limit bandwidth hogging applications - you can even tell the router to give priority to your gaming computer over everything else in the house if your router has that capability.

XIV sips data, and the connection to the queue server is just a small echolocation, a few packets. If those packets are lost or delayed, it's enough to cause the 2002.