Think outside the box. It's probably not to decrease the load. It's more than likely to save themselves from further issues when this month is over and everyone starts paying to play. The subscriptions are going to be one character for 12.99 or eight characters for 14.99. They have probably set this restriction in place to contain the amount of alts they'll have to "clean up" or restrict game play to. They already have a lot of alts that were made during open beta that they will have to restrict access to. They probably assume a lot of people will make a lot of alt and when time comes they'll end up paying for only one of them. So until that time they probably just want to keep it as clean as they can.