I have the same problem as many others here. Heavy lag spikes, since about 3 or 4 days. Other online games run fine.

Name of Internet Service Provider (ISP):
Deutsche Telekom

Country of residence:
Germany (near Berlin, to be more exactly)

When does the problem occur (e.g. only during specific times such as in the evenings?):
All day. It seems to be heavier during busy times, but I'm not sure.

Frequency of problem (e.g. every 2 minutes):
Varies from 1 second to 1 minute

Game content in which the issues occur (e.g. dungeons, trials, certain areas):
Everywhere. During dungeons those lag spikes are horrible. But it is annoying even when I'm crafting.