After weeks of additional development, Questie v1.0 is finally out, lots has changed since the last version, so much that the original post and youtube video is no longer accurate.
Currenly, Questie uses Cartographer for world map waypoints, and it's own internal minimap system to display waypoints on the minimap. It makes use of some data dumped from the 2.4.3 QuestHelper, and some data scraped from various vanilla wowhead clones. All the development is public and available on github, and any bug reports or contributions there are more than welcome!
Here are some example images of what Questie can do: