Sometimes I have a difficult time following dialog on TV. My wife and I leave the captions on for some shows just so we can hear some of the dialog. Sound must not be as important in TV as it is in film, and enunciation is awful among some actors. Some of them sound like they are mumbling their way through a script. At first I thought it was my hearing, but I had it tested. Plus, we have watched TV with others who are rewinding just to hear something again. In business, closed captioning services should be flawless. However, sometimes they are worse than the spoken dialog.
Yes, I feel for those who are doing the work of captioning. If they just need to work from a script and the actors stuck to the script, then it should be easy. However, TV acting is a lot of impromptu stuff. A script might not be any help for some of the dialog that makes it into the final cut. I have seen so many caption fails it is ridiculous. This is why when we were producing some video work that we chose a company that was a lot more meticulous about correct closed captioning services. Since we were paying to have it done, we definitely wanted it done right.
For our production we did not have any mumbling actors. Those who can hear should not even need the captions. However, for the hearing impaired, accurate closed captions are extremely important. The captioning should get all of the dialog correct, and interject notes about music being played and the mood of it along with any important sounds or non-verbal noises in acting. This is what helps make watching the production enjoyable to those who are hearing impaired and who rely on closed captioning.