Hello Friend,
I do transition consulting for NetApp, and it is fair to say the OnCommand product team also agrees with you and is working on exposing more counters.
In the meanwhile you can take a look at Graphite as a third party tool to accomplish this. Some ports have been opened up in OPM to facilitate communication with Graphite.
OPM opens port 2003 for Graphite inter-connectivity:
Links about setting up Graphite:
http://www.dburkland.com/how-to-setup-graphite-to-visualize-oncommand-performance-manager-data/
http://transitiontactician.com/?p=58
Graphite View:
Alternatively, if all you are after is network utilization you may check with your networking team to see how they are monitoring their network infrastructure. Network centric tools such as cacti may already have this data if the switches are being monitored.
Enjoy,
Hadrian