I don't think it's a big deal, although I didn't do it. I took an honors chemistry class that was 25 students as opposed to 600 (best course decision ever) and I felt very comfortable getting recs from both professors, since they knew me both in class and from office hours. One of my profs actually asked me to write HIM a recommendation letter for a distinguished professor award--I was honored.
It's annoying to have to take another class to get a LOR, but look at it as an opportunity. You need to get to know the professor anyway, so you might as well take an interesting class that you'll be able to learn a lot about by going to office hours, asking questions, and being vocal in class.