QH never should have had the routing, frankly. It should have a been it's own dedicated addon, and I think the same goes for the new API. Someone should just make an addon that plots the routes for you. If Carto Routes is standalone that'd be fine, but it requires Carto doesn't it?
And as for waypoints, the new stuff puts them on your map for you. Clad was talking about adding stuff to TomTom to make the arrow work with those waypoints.
Tekkub, Cartographer_Routes requires Cartographer, and is an abandoned project since about 1.7 years ago.
Routes is standalone, works with any and no map addon, and is maintained by me and Grum.
Routes takes data from many existing addons, but it really just does TSP on them. Questhelper's routing is far more complicated, because it more than does TSP - it also considers that there can be more than one location to complete a quest and picks the closer/better one, and also considers quest dependencies into its calculations.