I've been having these lag spike issues since the 2.55 hotfix that raised our weekly Poetic caps. It only happens weeknights during peak times, and I went from Gilgamesh to Balmung having the same issues. Check my internet and that doesn't seem to be a problem, modem works fine as well. But seeing as both these servers are on Aether, maybe it's a data center problem?

Has SE addressed this issue on other threads?