This is an 8.1 Update 2 setup, but the client does NOT have xDB (although we set up the Mongo connection strings, etc). We were getting 500 errors when hitting the Form Reports section for the APIs using the default analytics provider, so I switched to the SQL provider since xDB wasn't in use. That's working to fill in the Summary tab and to allow for exported data, but the Detailed Reports tab is coming back with "no data has been set."
When I look at the WFFM database in SQL, there are only two tables, one of which has fields with a ContactID and InteractionID, which have GUIDs filled in. I assume this would be the data saved to Mongo if xDB was running, but without it, those IDs don't appear to be otherwise used. I have the VisitorIdentification tag in the layout, and Analytics.PerformLookup is set to true. I also set my local session state expiration to 2 minutes in web.config to flush out the session.
If xDB isn't part of the license, is that Detailed Report tab essentially unavailable, since it requires the Contact and Interactions information from xDB?