Mjolnir is a potent tool against the likes of Stephen.
I'd personally give it to Thor 6-7/10. Strange could take a few wins, either after a grueling fight or he could pull off a crazy high end feat (under his own power and without context) and best Thor. Thor generally has all the right tools to beat Strange in a straight up fight, though, imho.
The electrical storm stopped him from being able to use magic, so that.
Plus if his auto shields protected him there and he was still almost KO'ed, then I'd hate to see Thor's severely enhanced lightning against his auto shields.
If he loses focus to attack his mind, then he gets his physical body destroyed.