What pretentiousness.
FOTM doesn't mean most overpowered class. It means most popular class. If all the classes were mathematically balanced there would still be FOTM classes. All it takes is a couple good players playing a class with a measure of success against the swarms of below average players. That leads to ill conceived balancing and the class weakest against the new balanced class now has an edge no other class has.
I would bet if all the classes were exactly the same, only difference being names, animations and ability names, same utility, same damage, same healing capacity, you would still see massive nerf threads and rage quit posts.