Maybe time for some merging?
The Important question is:
Do the players spend enough Money FoK?
The population does not really matter. No money= no Server.
Players can always choose the look for new adventures in other servers. There are Server Transfer events where u can more or less for free change Server and also u can change server anytime you want for 1000IM if u contact the support.
FunofKing is my true hero