I would be curious what Ian Woosnam's numbers would have looked like at his peak in the late 80's early 90's. How about Norman at the same time?
Norman's driver clubhead speed (wtih a 43" steel shaft) was clocked at 121 MPH in the mid 80s. I'm going to assume that was him maxing out, not his typical swing. That is about what the leading player on tour averages today with a light weight 45"+ shaft. However, that is their average and they peak closer to 130 when they want to.
With that type of potential max clubhead speed, Norman was averaging around 270 total yards and he got about a 13 yard spread over the tour average.
Based on his ball flight, it seems as though he was losing a lot of distance due to high spin/ drag. I'm sure he was losing more because of the lack of trampoline effect and the ball turning to mush on him. In his peak form, he probably would be near tour leading with today's equipment, so he'd be getting about 40 more yards with the same ability- about a 15% increase. That makes a 7,000 yard course in 1985 equal to an 8,000 yard course today. Since courses haven't kept up with inflation, the game has probably gotten easier from a pure length standpoint.
The spread between the longest drivers now and the tour average has increased. The diminishing returns that players used to get have lessened.
It was interesting to come across an account of Lido as being considered a "he-man's" course due to its length. Also interesting are accounts from the early 1900s about how distance was making courses obsolete. So, this battle to save the classic courses is nothing new.