diagrams invariably show only 2 dimensions, so you can't reasonably show anything that has complexity in more than three dimensions, which means any problem with three independent variables is out. Animation can add the missing dimension; well color can, too.
I'm cautiously optimistic about VR as a tool for teaching and understanding math up to three dimensions. You may have seen the "Non-euclidian virtual reality" video floating around YouTube (https://www.youtube.com/watch?v=ztsi0CLxmjw).
