What basis do you have for believing that this is the case?
Cause you don't exceed bandwidtih on all at the same time. Some would still be logged in, if your pipe is 100 and you have 12 that each use 10 then 2 would go out but the other 10 still be ok. So if all are disconnecting at the same time I would assume its Blizzard, which must have such protection for DoS attacks and to stop 60 box gold farmers.