I am level 49 now, and around the 4th/5th year, I noticed the AI became a challenge. At that point, I started racing S-class, and noted I have to bump my way to the front very quickly in the early stage of the race, or the leader just gets away with the few laps the game has per race.
Aside from that, I have *very rarely* had the AI dive bomb me. Also, I really try to pressure the AI into making a mistake and NOT hitting them.
If you are having a problem with the AI hitting you, have you hit them before? I feel like this is a learning drivatar you are competing against, and if you are bumping and banging with late braking into other cars, guess what -- they are going to hit you too. If you race clean and don't touch them, I have seen them always get out of the way, or take evasive action if I brake harder then them in a brake zone.
Please note I am playing with zero assists (Expert) in the 4th/5th season with S-Class and A-Class cars.
Other than having to get to the front fast with a RWD, I don't see the AI as the problem. I have been the problem, and I do get some AI taking revenge on me, but the car I have chosen and modified always has the legs in the straight, and I can always outbrake in the brake zones.
2007 Subaru Impreza Forester Sport Cross World Rally Blue/Gold BBS wheels RP4 rally/STU autoX
2006 Subaru Impreza WRX , San Remo Red/Gold -- STU/NO4