Lag spikes

The 8% reaching our servers is what matters (the 42% will just be the node prioritizing other packets over ping attempts). Did you run this trace while you were playing on this gateway? Do you get the same packet loss playing PoE on a different gateway?

Hmm. There's a hop issue on your first EU trace that seems to indicate connectivity issues, however there's that same hop on your trace to the US gateway without the same packet loss. Additionally, your first trace has not indicated your reported spikes to 300 or 900 ping.

Are you still experiencing your connectivity issues on the EU gateway? You may need to instead try running a PingPlotter trace next time you experience this connectivity issue.

Thanks for the most recent reports. The concern with those 300-900 ping spikes was that they were not captured in your traces, however it appears this is the case with your most recent traces aswell. Assuming that these traces were taken when you experienced these ping spikes, these traces just aren't capturing these spikes.

Do you share your connection with any other users? Do you experience these latency spikes during certain times of the day or in specific areas with specific monsters/skills?

I'd check that your Antivirus/Firewall is not interfering with Path of Exile's connectivity, and using a wired connection to your modem/router while you test this.