Just bought the soundtrack for the expansion and I'm thoroughly disappointed. Marty's absence is already starting to show through the lack of memorable motifs. The best track is arguably the Sepiks Redux, which is just a sloppily orchestrated cover of the original with electric guitars thrown over top. it's hard to fuck that up. The title theme for the expansion itself seen throughout the soundtrack has some weight and is well written despite being safe and generic; it's comparable to a free to play medieval MMO's title track. I guess I could say the only other stand out themes are Elegy and the very beginning of Young Wolf as it loops beautifully in the Temple, but then the track itself goes off the rails into an obnoxious march, which seems to be a pitfall about 70% of the rest of the soundtrack falls into after it introduces a promising melody. In the context of the game, they work as "cinematic background noise" for action sequences, but one of Marty's staples was blending that necessity with melodies that were still recognizable. All I hear is a mish mash of percussion and string riffs I'd expect from amateur composers who think tthat's all there is to cinematic action music. That's weird to me because Michael Salvatori should know the deal by now. I hear his signature style throughout, but he's clearly lacking the anchor that Marty was, and on its own the staying power of these cinematic themes don't reach movie levels, which I could at least say for Halo 5's soundtrack which also experienced this problem.
I'd honestly be worried for Destiny 2's soundtrack at this point if there's a chance the original motifs are going to be replaced. Very few themes added since Marty's departure stick out at this point. I'd have no reservations saying the majority of this expansion's score is noise.
edit: here's the soundtrack link
https://www.youtube.com/watch?v=PfrtX-foWUA
Compare anything here to the excellent arrangement and instrumental complexity seen in The Union.
https://www.youtube.com/watch?v=qkNBJsx3WLs