I don't know if anybody else has a fair amount of network interfaces that connect to devices that you don't care about (ie end user ports)! But with NPM/NTA you have to poll the interface in order for NTA to show you the graphs of the interfaces. This might not be the ideal setup for 200+ user ports on 1 switch. This is an estimated 80 snmps/150 mil seconds with a 2minute poller setting. The work around that I found was on the ports that I don't want to poll, but what flow data from was to Unmange all of the ports until 2020 and set a calander reminder to change in 2015. With the interfaces in the Unmanaged state NTA still gathers/computes the data for the interfaces, thus giving you visibility into the network with out consuming switch resources via SNMP polls.
Hope this helps somebody else.
Don