said by Rhenai:Log in queues - I started off in Dalaran, and every year, like clockwork, between Christmas and New Years, you could plan on waiting anywhere from a few seconds to 15 minutes just to log in; the free character transfers to less populated servers were offered many times. Honestly, I have not run into queues in a couple years, so must be that they got something right 
(Granted, I hardly ever visit my toons in Dalaran, so maybe ignorance is bliss. Anyone else on Dalaran??)
Queues on Kil'Jaeden on MoP release were 2+ hours. I'd literally queue when I got home from work around 5 and it'd be ready when my son went to bed at 7.