Did this resolve, Akylio?
World Server means a specific region within a realm. Eastern Kingdoms, Pandaria, etc.
Normally when one zone is unavailable the area reboots and it comes back fairly fast. If you are having issues in one area, that doesn't necessarily mean they are all unavailable. For instance, if you are in Pandaria - and you have characters in Eastern Kingdom they may be able to log in just fine.
Typically the longest one of these takes to self-resolve is 5 - 10 min. Any longer than that and something else may be afoot.
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