So I discovered a limit in Visual Studio. It apparently doesn’t handle 1.4 GB of data in 40,000 files in a web site very well. I killed the process after it was "Validating the web site…" for over an hour. I finally figured out I needed to build a smaller Deep Zoom image for testing just to get the build time reasonable.
I wish there was a way to make it ignore that directory for the compile step.