Enable session tracing (you can find it in the NCM settings section of the web console)
Login to the NCM server, and launch the Network Configuration Manager win32 utility
Choose your device, and initiate a download manually
Image may be NSFW.
Clik here to view.
The session traces can be found under C:\Program Files (x86)\SolarWinds\Orion\NCM\Session-Trace
That should reveal where it is spending the most time to download