I introduced XD to our designer today... the first and what I would think would be obvious, was; how do one go from the "design" and "prototype" phase, to development. In Photoshop, one can easily create the graphical assets (images) needed to build out a page.
I would expect something to facilitate that flow - whether that be an export of web optimized image, or export of an Artboard to Photoshop (or both).
I'm not finding a word about that obvious "next step" in the development cycle in documentation or intro material.
The bottom line is, the incentive to design in XD is pretty small if one must redesign an entire layout in mature environment like Photoshop to create those assets.
You might want to check out the export workflow, which allows you to export multiple sizes for your developers: Learn how to export production-ready assets from Adobe Experience Design as PNG, SVG, and PDF files.
You might also want to show your devs how to use the measurement tool: Learn to draw simple lines and shapes using the drawing tools in Adobe Experience Design.
We're also working on a more robust developer handoff system. We shared some of our vision at MAX: Adobe MAX 2016. Day 1 Keynote (Chapter 3) | Adobe Creative Cloud - YouTube (start around minute 22). If you're interested in this, you might want to upvote this in UserVoice: Generate specs / measurements / style guide for developers – Adobe XD Feedback : Feature Requests & Bugs