Use “queue tree” instead of simple queue. simple queue is best for distributing bandwidth equally among users, queue tree is for prioritizing.
You can also check this topic: http://forum.mikrotik.com/t/fasttrack-friendly-qos-script/102401/1
(the reason it does not work at all is likely that you have fasttrack enabled. that is not compatible with simple queue. it is compatible with queue tree, however)