is the nexus' L3 in the global (default) vrf?

if *not* then it won't (easily?) work until cisco fixes the (being kind here) "oddball way" that mib exposure happens on the nxos platform. 

a workaround could be to map out things with snmp contexts that tie in a string per vrf ... but imo that doesn't scale effectively. 

join the party:  go beat up TAC and your sales rep. for how stupid their implementation -- of something pretty fundamental -- is. 

luck,

R. 

  Typogaphical errors courtesy of iPhone