My diagnosing of the issue has just been running tracerts and winMTR to the oceanic wow server ip and seeing latency spikes to certain hops, including the last hop at times. I have tried running ping in cmd and noticed dropped packets at times where the connection is particularly bad. I see this on all devices on my network when packet loss is occurring.
This is just what I posted in my first link. It is normal to see spikes on a traceroute, as-long as your end destination is what you call acceptable then you're fine.
What Fibre plan are you on? You mentioned it is only at these specific times, do you have something like a Torrent app running chewing up all your upstream bandwidth?