Had to do some searching to figure this out, so I’m noting it here for future reference. Even though smbclient -L works just fine, mounting with smbmount or mount -t was just not working.
apt-get install cifs-utils
mount.cifs -vv //192.168.0.3/backup /mnt/drobo/ -o user=Admin
it prompts for Admin’s password, then voila.