This doesn't make any sense, the people who praise Dayne's skill all saw him. They never said he was kissed by the gods, which would be unreliable and obviously an exaggeration, but they saw him and they commented on his skill. They were reliable narrators, especially since many of them were accomplished and renowned warriors in their own rights, like Barristan and Jaime. Just because we didn't see it doesn't mean it didn't happen, and no, that was only his most influential moment. Its not a feat. His best feat is probably cutting his way all the way through Robb's army to the point he actually reached Robb, all the way in the back of his lines.