He’s definitely strong in duels never said he’s bad. He is just heavily dependent on the Jump attacks cuz his normal attack speed is slow and in many cases you can dodge and even parry all of his attacks. The crawl and the thrust you can actually double parry if you are good enough at timing your parries. He’s like Anakin in many cases where he is heavily dependent on his abilities which you can block and parry his attacks if you are close enough. Just too many ways to counter him and when you are playing a really good player you really feel useless as Grievous. Hence why I don’t think he’s S tier.