As per a news annoucement by James Nichols from Mythic Customer Service:

Hello everyone,

There are currently 4 servers on which players are experiencing high wait times. All other servers currently have no queue at this time. Players are strongly cautioned against starting their adventures here if they can play elsewhere. All four of these servers have had the number of concurrent users they support raised to the maximum possible.

The servers are:

Volkmar
Skull Throne
Badlands
Dark Crag

Thank you for your cooperation. Have fun!