Queue is not working fine with high bandwidth

RouterOS General
1

I’m using the simple queues to shape traffic of my servers ( cause I’ve only a 100 mbps link and I should manage it )
It’s working fine for each IP to be shaped at less than 1Mbps speed but when I increase the limit to something more than 1M it cause the real usage bandwidth of each server to be less than 500K, so while I’m trying the increase the speed of a specific server it decrease the speed.
usually I need to shape traffic of each IP between 4Mbps and 30Mbps
Any suggestion on what can be wrong?

[admin@MikroTik] > queue simple print
Flags: X - disabled, I - invalid, D - dynamic
 0    name="74-20" target-addresses=xx.xx.xx.20/32 interface=all parent=none
      packet-marks="" direction=both priority=1
      queue=hotspot-default/hotspot-default limit-at=0/0 max-limit=64M/64M
      burst-limit=0/0 burst-threshold=0/0 burst-time=0s/0s
      total-queue=hotspot-default
2

What does the ping look like when the speed reduces?

After you read this and apply the know-how to your setup, do you find a solution? http://wiki.mikrotik.com/wiki/NetworkPro_on_Quality_of_Service

Thank you.