After many hours of trial and error this is my take on fixing the AI-behaviour at the Nordschleife endurance track. Tested with the Porsche 962C ST, Porsche 917/30 and all GT3 cars. AI pack of 23 cars at 100%, no mechanical failures, air temp at 0 and then at 36 degrees Celcius again. They will now negotiate the track without major clashes or crashes anywhere. Qualifying laptime of the Merc AMG GT3 is 8:58.3 which is noway near the IRL qualy time of 8:11 minutes at the 2016 24H, but well, you can race them. I guess this is strictly for offline racing because of changing the ini files (possible server mismatch). All griplevels (grass, kerbs, asphalt and concrete) are set at FRICTION=1.0 to keep them on the optimal racing line (especially at T1 and the Karussells). They do however break late and deep into the corners and are on average 20km/h faster in the chicanes.
Back up the original files surfaces.ini and ai_hints.ini which you can find at the following path: assettocorsa/content/tracks/ks_nordschleife/endurance/data folder and then install this content file in the assettocorsa folder.
AI-fix for GT3 and Le Mans racecars at Nordschleife endurance. 1.2
Proper offline racing against the AI at the Nordschleife endurance track.