Really, to be a good captionist you have to be on that level.
When I was a captionist, I found the hardest calls to caption accurately were ones involving Jamaicans. Besides talking fast, their syntax is very different. I used to joke, and not even really kidding because it was true, that my nightmare call is the jamaican conference call. Yes, sometimes I had to caption more than one speaker at a time. Yes, sometimes they were all Jamaican.
Really was a nice job though, great benefits. My biggest complaint? Listening to thousands of hours of peoples conversations can be very mentally taxing. It is hard to keep prayer doing that type of work.