I think that's one of the reasons I like the Dresden Files audio books. James Marsters is an actor, not a narrator.
I can't tolerate the discworld audio books after the first two because of the awful voices, sadly
Try one of the later ones
There are two types of Discworld audio , the abridged versions are all read by Tony Robinson (and are normally only about 2 hours or so)- the full unabridged early ones are read by either Nigel Planer , or Celia Imrie
At one point they changed and had them all read by Stephen Briggs (friend of Terry and the person who adapted a lot of the books for the stage) , he still 'does the voices' as such but they sound a lot better (to me at least) - from a quick search it looks like he took over around book 24 (The Fifth Elephant) so give one of the later ones a try.
There are some dramatizations but they do tend to be very abridged and you lose a lot from them (the radio 4 version of "The Amazing Maurice" is one of the better ones out there).