I have a fair amount of instructional experience. I was a sqn cdr at Linton and also the stnds cdr. I was also heavily involved in the work on the infamous TV film. In my opinion a very large percentage QFIs tried to do their best and would come to me if they thought they were having a personality issue with a student. I also got good feedback in the bar on a TGIF thrash. I think I would have soon learned if airborne bullying was taking place and would have jumped on it pronto. The nearest it came was when one student was having serious problems. So I reallocated him to one of my best (most successful) QFIs. After I had briefed him he asked "OK boss, do you want me to teach him or set him up" He was not serious, worked hard and the student graduated.
On another tack, I have also done a fair amount of civil instructing at a large school. IMHO the standard there was far below that in the RAF with very little empathy with the students. I became so dissatisfied with what was happening that I decided to get out of it and become an airline pilot with Air Europe. Pity it went bust.