I'm really confused. Did Joe get thrown out of class or not? What happened to the dean-person you talked to who said he would look into it? I'm lost.
On the other side of the coin...honestly, I simply wouldn't tolerate this any more. You can't control Joe, but you can control what you do with your time and education.
I was once in a recitation class (small group class with TA attached to a very large lecture type class). Within one class period I figured out two things. One: the TA (graduate teaching assistant) had no idea what was going on (I think it just wasn't her area of expertise and also perhaps she was assigned the class at the last minute) and two: there were some VERY annoying other students in the class who were constantly whispering and chatting and being generally disrespectful. I have pretty much zero tolerance for that kind of behavior. This was also a class in my major (Religious Studies) and I wanted to learn a lot. I also knew my own personality and tolerance for obnoxious people and knew being in that class would raise my stress levels to unhealthy levels.
I went to the TA immediately after class and basically told her that the students talking in class was going to drive me nuts and I was serious about learning, and I was going to try to switch to a different class. (I decided it was unnecessary to tell her I was pretty sure she didn't have a clue about the subject matter). She understood completely and said it was fine. I got out of there and into a different group with an absolutely fantastic TA. And, I learned so much.
After the first few classes of Joe disrupting it and the professor doing nothing, I would have been out of there. I would have switched classes or just dropped it altogether. But, I would have made sure the professor, the dean, the guidance counselor, the president of the college, and whoever else knew exactly why. I strongly worded letter that I felt forced out of a much wanted class because the professor refused to handle the situation.
I'm pretty perplexed that the professor allows this. Any one acting like that in any college class I have ever taken would have absolutely been thrown out of class.