You want to point the DFS leaf at the cluster using \\<isilon_static_smartconnect_zone_name.fqdn>\<sharename>.
So here is an example in my demo lab:
Step 1. Create the Namespace (as Domain based):
Step 2. On your Isilon cluster, create the share:
Step 3. Set the NTFS and Share Permissions appropriately, I won't delve into how to do that for this response. Also put a few sample files in the directory, just so you can be sure it's working:
Step 4. Create a new Folder in DFS, aka a Leaf:
Yes if you hit browse at this point you will get an error in newer versions of Windows Server (:
Step 5. Ignore it, and just type in the name of the share that you know you created:
Step 6. Click OK a few times. To quote Emeril, Bam! done.
Step 7. Browse to the UNC path, in my case as the domain admin, because I used run-as-root permissions and didn't bother setting up proper ACLs, or real data, because it's a lab.
Step 8. Ensure that the data you created or that was already there is visible:
So; TLDR; Ignore the error and just type in the full path and hit OK. Or you can use powershell to create the DFS leaf without messing with a non-working browse button that expects the target to be a Microsoft Windows server. There are plenty of threads on TechNet about this issue, but not worth your time to be honest.
Hope this helps, if it solves your issue, please mark it as solved/resolved.