Another Pathfinder main here. Yes, he's been both passively and actively nerfed almost since season two. If they're not actually downgrading his abilities then they're giving them to half the other legends, and I'm not just talking about survey beacons here. In the beginning he was the go-to legend for reaching unreachable places on the map. Now how many legends are there who can get to high places with the push of a button? Octane, Loba, Ash, Horizon, and Revenant. Oh, and Valkyrie can bring her whole squad while getting the real-time location of enemies everywhere? Ridiculous.
And you're right that Pathy's ultimate fails to work properly about a third of the time - especially aggrevating when you're trying to use it in a pinch. I've never seen Valk have an engine failure on take off.
The problem is that buffing and nerfing of legends has nothing to do with balancing gameplay and everything to do with balancing pick rates. This is why Mirage and Valk and ridiculously over-powered and poor Pathfinder may as well not even have abilities for as often as they actually work or aren't instantly countered by some other op legend. Like Valk. Who needs to be removed from the game. Not nerfed. REMOVED.