I have 3rd beta 9.2 and everything is way too quiet except movies are crazy loud. They haven't figured out how to get audio out of the new speakers consistently.
It's not fixed in 9.2 beta 3. But I also wonder if it's intentional. I don't want my keyboard making the same volume sounds as music etc. I have all those sounds off anyway personally.
I have the problem with my iPhone and iPad pro too but with the keyboard clicks it's too low hard to hear when in full volume, called Apple restore to factory reset, NADA I believe it software problem.