Well you just explain that you’re playing World of Warcraft and you experience severe lag spikes, and the time of day it happens and for how long.
If you want to be fancy about it, you can do a traceroute and provide that. Someone did that in the other thread:
WinMTR is a program you can download that creates the traceroute.
But I would say that it’s sufficient to simply say that your internet is not operating as it should when you’re using certain applications at certain hours of the day and it’s been ongoing for a period of time.
You don’t need to be a tech wiz to complain about a product. We don’t need to be that with Blizzard’s product, so why should we with other ones?