Remote disk management on Server 2012

Solution 1:

Nah, it's just me being a blockhead - I was using a management station which did not have the firewall group rules for Remote Volume Management enabled, although I was certain it was the case. Running

netsh advfirewall firewall set rule group="Remote Volume Management" new enable=yes

on the client fixed the issue. So RPC for volume management has apparently not been deprecated (yet).