I haven't personally tested this out but wanted to throw it out there. Argon Garrison on the new map seems to have a bunch of mobs close together that appear to have a fairly short respawn rate. When attempting to do the historian escort, it felt like it was maybe around 30-45 sec respawns. Perhaps a group could circle the garrison clearing mobs and they'd start respawning by the time the a loop was completed? Just a theory.
I'm not sure what the VM/hr rate would be if it could be farmed consistently there and how it would stack against Istan's meta chests.