The lag is still horrible all around. No way has this gotten any better... If you find lag (not talking about spikes either but minute long ) of <15 fps acceptable then good for you.
Loading times are still absurdly long... Nothing has improved there. I frequently stare at 2-3 mins loading screens.
If that is true, i wonder if there are perhaps some problems with your ps4?
I am very sure performance has gotten better with the patches for me. Before the patches, when i was in the bog, the framerate was annoying. The first time i got around crow perch, the framerate wasn't all that either. Everytime i started raining, the framerate dropped badly. I'm not lying when i say this has been a lot less for me. Played all evening today, and there were a few occasions on where the framerate dropped, but nothing grave.
Also, whenever i load a game, it's within a minute and certainly doesn't take 2-3 minutes.