One of the problems with voice acting, is that if a mistake is made and not caught, it can pull you out of the immersion. For example, when you click on a globe in the game, the narrator says 'And you thought Rivellon was flat'. However, he puts the emphasis on 'Rivellon', making it seem that he's comparing how flat Rivellon is versus some other place. He should have put the emphasis on 'flat', emphasizing that Rivellon isn't flat, despite what people believe.
I did specifically notice that one: overall I thought the voice acting was good and added a lot to the game, though I do sympathise with what you're saying. Not least as I absolutely
hate Peter Jackson's interpretation of Lord of the Rings, for example, and think that compared to the original written work it lost far more than it gained in the process. But that said, Tolkien's work was intended to be the written word whereas OS2 was most likely intended to be acted from the outset, and I think the matter of which medium is better is a much more gnarly and subjective thing than the pitfalls of trying to convert one to another.
