So when I add a new host to the cluster should I expect NFS datastores that have been provisioned using VSC to be mounted to the new host? or is further action required to give that host access to the NFS exports?
If they were created with VSC then there on the export permissions for the volume the IP address for the vKernel ports on all your ESX servers will have RW and root permissions. Just add the vKernel IP of the new host to this list and then manually mount the datastore from vCenter.
This type of update is on the roadmap for VSC just so you know...
The easiest way is to use NetApp Systems Manager, then click on Exports and then the NFS export. From there you can edit permissions and add the IP address.