Hi Rob,
Yes, this is certainly a valid flow scenario for forms that submit to DBXL where SharePoint workflow is also involved.
I'm assuming that you have turned on property demotion for your fields so that you can edit them in SharePoint. This feature is turned off by default and it is not a best practice because SharePoint doesn't validate the XML data types like InfoPath does which means invalid data can be entered and then the forms may not open. However, for simple string data types, it shouldn't be a problem.
If this is the case, and you are using property demotion - the XML will be updated when you update a column. However, that XML update won't flow back to DBXL unless you have a workflow trigger to submit it or use our new DBXL v2.8 SharePoint event receiver.
Having the workflow submit the form when a column changes can be done, but SharePoint workflows don't support out-of-box Web service submits. If you are using Nintex, you can do this but the modified by information may not show the correct user because Nintex does not impersonate.
Our DBXL v2.8 SharePoint Event Receiver is currently in beta. If you'd like to test this, please email Support [at] Qdabra [dot] com and we'll send you instructions.
The official release for DBXL v2.8 is now looking like early May. We appreciate your patience.
Best regards,
Patrick