TFS WorkItem Viewer will enable you to select an iteration of your currently active Team Project and to visualize the dependencies between them as DGML. It is fully integrated into the Team Explorer (Work Items -> Visualization) and is very easy to use.
At the moment this tool is in Alpha state. We will provide more informations on our blog soon. Your Feedback is welcome!
Please visit this Gallery-Page for the 2013-Version of this tool.