What am I missing to get symlinks to work with CIFS?
Not sure, but I fear that a cifs share, that in your case is essentially a folder on a ntfs partition available through the network, cannot manage symbolic links.
Different would be the case if the cifs share were provided by a samba server on a linux machine.
The solution that come to mind is:
- create a huge enough file on the share (with dd, for example)
- create a ext4 filesystem on this file
- mount the file as a partition image, with -o loop
- use this ext4 partition as a destination for your backup