This problem could obviously be solved by simply removing unnecessary servers, and use the broken populations of those servers to flesh out the ones that can be saved. Give the people a number of Standard/Low server choices to move to. The people who have failed to choose a preferred server by the end of the month or whatever, gets tossed into the server than needs them the most.
This thread is basicly my response to this thread: http://eu.battle.net/wow/en/forum/topic/2986509135
I figured it could need some more attention than being Post X on page 38, considering it actually offers a possible solution rather than just ranting(not to say I don't agree with that rant).