As it seems with the BS and their current lack of run time, this is only due to server population, and trying to make them run more, one way would be to merge some of the level ranges, not seperate them more. This simply wont bring more people to the game, but everyone seems to want their twinks on top of the food chain, and still not pay the price of having the BS actually running.
How ever much you tweek the ranges, no more people will play for now, so my suggestion would simply be, allow the BS to run with 2 or more people from each side. This should solve many of the problems, and create a few new ones, but atleast the BS would run more, if not a bit slower and purposeless at times.