The process of providing the best information for technical people, end users and power users is improving and along with it the location on where all this knowledge is being curated has changed.
For V8.x and earlier content, find it at TechNet. The MSCOM content (Help & Training) has been moved to TechNet so you can access end user and admin/customizer in a single place.
What about the Dynamics 365 Help and Training site? That’s being shut down and will be gone by the end of November 2017.