@ daanji

WoW progress might give a better view on population and activity, it basically counts the toons that have cleared a raid boss:

server specific: http://www.wowprogress.com/pve/us/magtheridon (based on guild T13 raid progress)
us realm ranking: http://www.wowprogress.com/realms/rank/us (based on T13 raid progress) - as you can see magtheridon is #30, and it also displays the horde/alliance ratio and total logged toons

It basically gives a pretty decent indication about how a certain realm is in reality, much more than warcraftrealms. For example a realm that has no raid progressed alliance guilds at all, will turn out to be pretty empty if you visit it.