I've been playing on NA servers mostly the past months. This weekend I went back to play on EU servers actively and oh boy, was I amazed to see just how long it takes for any of my 15 chars to load into their zone !!
I don't know if this is a back end resource error on the servers that host the zones or a network performance problem but the difference is night and day.
As soon as I switched back to the NA servers I noticed these problems are not present on that platform.