Sharepoint - Using TFS and SharePoint Designer

There isn't much you can do to improve this workflow, although a stand-alone TFS client will make it a little easier. SharePoint Designer is a great tool for working with artefacts and customizations in the content database, but is not really designed to work as a development environment. It needs to work in the context of a functioning site.

You also need to be clear about which items will be source controlled as development artefacts, and which will be content. The latter will be versioned in the content database. Not everything needs to be in source control.