The Orochi has little damage. The reason they are good is because they have a lot of combos that can deal damage. That's all. The main way to beat an orochi is to play more defensively and not give them the edge. As well as Guard breaking. If you can break his guard and get in close enough to hit him with one of your combos, he will be dead in the water.
People just need to learn how to fight them and not just claim overpowered. Playing an orochi I think the Raider is overpowered because in one attack he can take 1/2 my health. Followed by a combo I'm dead in 3 hits. It takes at least 6-7 hits from me to kill someone.
edit: Assassin classes are supposed to be quick and deadly, they always have been, but they're glass cannons.