Sure you can backup the shares in BE directly... But it's slow, terribly slow. You dont need to mount the shares like in NBU (which btw you notice they only talk about NFS) Which screws your Windows clients ;)
I cant stand NDMP and it's so restrictive.. But there isnt a better way to offer faster backups.
The best you can do is use all the ports in the NetApp if it has multiple ports, and just backup the CIFS shares over the network. 'Bout all you can do is get as much bandwidth out of it, as CIFS is terribly inefficient.