You probably need to specify what view(s) the group has access to.
Assumed to be every object belonging to the Internet (188.8.131.52) OID space, unless the user uses the read option to override this state.
Additiona information; http://www.cisco.com/en/US/docs/ios/12_0t/12_0t3/feature/guide/Snmp3.html#wp19564
The view I created was being applied properly for read and write permissions. It looks like it was just too narrow.
I modified my view:
no snmp-server view OrionNPMView mib-2 included
snmp-server view OrionNPMView internet included
Now I'm pulling in everything I need. Thanks.