The main reason I recommend NOT repeating text in the audio is that most of us read quicker than we speak. This means that for any text more than just a few words, the learner will be out of synch with the narrator - resulting in them neither understanding what they are reading nor listening to what they are hearing. Alternatively, the learner slows their natural reading speed to match the narration, which results in frustration.
While I like to use audio, I find it creates problems which I feel outweigh its value. Ideally, narration should to be professionally produced - in a studio with a voiceover actor. However, budget or other constraints may not allow for this. A reasonable quality can be obtained with modern equipment, but this cannot compensate for the quality of the narrator - just because the designer can narrate, doesn't mean they should. Quality of voice and intonation is important. Getting the right narrator is one thing, but getting them back again at the last minute to record some client changes is a headache I have endured too often.