The thing I hate about these sorts of premises of finding a broken class or strategy in a game, is that the protagonists is almost always joining after it become popular so someone else should've found it a looong time ago. In the case of a class, people will play what they want to play even if it's suboptimal or bad, in the case of a strategy someone someone else definitely would've stumbled upon it. In online games, people are like monkeys and typewriters, they'll eventually find every single secret and strategy.