What lag? Where are you experiencing it and when? Where are you playing from and through which ISP? I haven't personally suffered any lag but if others are experiencing it then this sort of information can assist in finding a common cause.
Same, ping is getting worse since december...and i get around 3/4 DC in 2 hours now...before december i never had DC(not considering modem problems, but only game problems).
You're more likely to get a reply from the ZOS technical guys on the PC Technical Board (sub-board of the Community Support board), but I suggest you give them as much information as you can about which server you're playing on, your location, ISP, which zones you're getting lag in, provide trace-routes to the server, and so on. If you also encourage others to do the same then ZOS may be able to spot the common links, as clearly not everyone has the problem.
From what you've said so far it would seem to be an issue with the German network or possibly one German ISP, playing presumably on the EU server. Without more information tho' it's going to be difficult to pin it down. Have you raised it on the German language boards?
Is this lag in Cyrodiil only or is it in the PVE zones as well? Please keep in mind that Cyrodiil lag is merely ZOS' attempt to increase the difficulty level of the PVP combat in lieu of bug fixes and content updates.
We just had another huge lag spike in Cyrodiil moments ago. This is not a one-time occurrence. Players are getting very frustrated, including me. Everything freezes, though we can still move around, just with no responsiveness. They usually last about ten minutes.
To reiterate, I am playing on the EU server, from Germany. Every evening during prime time we get 20 second pauses where the game freezes. I do not know about Cyrodil, I am leveling lowbies.
Glenumbra (and of course Cyrodiil) is a lag fest on the EU server. I used to play on the NA, and there was pretty much never lag. EU is a different story.