Pretty much anybody that can reliably parry and isn't crazy offensive is a hard matchup for Orochi. He's got no good openers whatsoever.

A character that mashes buttons and constantly attacks is a much easier matchup most of the time. Orochi's not good offensively, but he is a counterattacker, and a nasty one at that if you use it right (and if you're lucky enough). Parry, grab, top heavy, feint side heavy, double top light, side light, zone attack. It's enough to bring most of the cast from full health down to critical health, assuming you manage to pull the whole thing off.

His rushing attack, or Storm Rush, is never a good idea if you're just directly using it against your opponent, regardless of what your opponent's actually playing. It can be seen coming from a mile away and the strike always hits from the same direction, making it a free parry or an easy block. The only times when that attack is actually useful is when your opponent either swings a very slow attack and whiffs it, or when your enemy is not focused on you or can't, such as in a ganking situation when he's being guardbroken by one of your teammates. That being said, if you actually land a Storm Rush, you get a free double-top-light. So use it wisely.

In summary, Orochi is the most defensive of the Assassins. He's absolutely horrible against a character who just stares at you and turtles. But if and when your opponent goes offensive, Orochi has a full arsenal of nasty punishes at his disposal if you use them right. Storm Rush is only viable when you're close to 100% sure your opponent can't parry it.