Johnny Miller torched Oakmont in the last round of the 1973 Open with a 63. The USGA overreacted a tad.
Oakmont is a brutal course. The course has removed trees and bunkers over the years to make it more playable. They slow the greens down from 14 to 13 for the Open.
But Miller played after a heavy shower had softened the greens and attacked the pins because he was trailing. He was in the zone. It was a rare situation.
Winged Foot is a very hard course, and the membership tends to be serious golfers. Their #2 course is highly rated as well.
The toughest conditions I saw in person were at Pebble in 1992. I knew driving in that it would be a tough day, because the overcast was gone. It was clear and windy. Very small, hard greens, winds of 30 mph, and deep rough. It was one of the highest scoring rounds in Open history. Woosnam, Floyd, and Simpson shot between 80 and 88. Tom Kite kept the ball under the wind and took the lead with a miraculous chip-in on 7. Meanwhile, Gil Morgan was over the cliff at 6. I was at Pebble in 2000 and 2010 also. God willing, I hope to be there in 2019. It's unsurpassed.