we have massive similar problems here each evening between 16:00 and 23:00 UK time but only for some of the regions or countries, don't know exactly. Some of my guild mates who are from western Europe don't have these issues, me and everyone i know that play from Romania, we all face the exact same issues. Massive lag spikes, major input lag all the time and also countless disconnects and being prompted to start screen many times without even an error message.
But i repeat, this all happens only during evenings between those hours. Rest of the time is fine. Too bad all guild events and almost every other activities happen mostly during those hours.
So far the forums have been littered with articles complaining about these issues, not one single official comprehensive response received. Nobody even bothered to reply.