Seems like you should add some extra help for the holidays like alot of other places do. i am sure blizz can afford it.
What can be afforded is mostly irrelevant and this has nothing to do with just the holidays. It has to do with the issues that come and go with online games. Like large content patches that often generate a lot of petitions.
Training a Game Master isn't remotely comparable to training temporary holiday help. At least in regard to any place I have ever worked. :)
As the issues/bugs are resolved after a patch release, and new systems are gotten used to, queue times return to normal.