Moved this to the NSP space for you.
Not sure if I understand your stats correctly, but the m1250 sensor can handle up to 100Mb/s total throughput. If you have the sensor in-line on a 10 Mb/s link and are finding performance issues, you may wish to check if you are seeing any CRC errors on any of the interfaces from the CLI on the sensor. Check your duplex and speed settings as well, make sure the switch or router/firewall are not configured for auto. Run a report on blocked alerts and see if any P2P based alerts are being blocked.