EDIT: Disregard, the talent tree endpoints are no longer 404ing and now return the necessary information, thanks!
Perhaps I’m just missing it but it seems the API doesn’t offer a way to get all the talents for a class/spec and their relationship to each other.
The /data/wow/playable-specialization/{specId} endpoint offers data for the pvp talents, but for regular talents the spec_talent_tree field just has a name and an href that 404s.
There is also the /data/wow/talent/index endpoint which lists all 2600+ talents, but only provides the name and ID of each, so to determine which class/spec they are for would require an additional 2600+ individual calls - which is doable obviously but not really ideal, especially since it doesn’t appear to provide any indication of where they fall on a talent tree (i.e. what prerequisites they have).