Solved
No audio & single player cutscenes are playing very fast.
Haven't played the game in a while, but trying it tonight yielded the aforementioned issues. Attempted to "repair" the game, no success. Very capable hardware, all up to date audio/video drivers.
Hilariously, uninstalling the Realtek audio drivers completely seems to have fixed the issue. Audio works fine for both titles, and the cutscenes are back to normal. Thanks for nothing Realtek!
