Welp...I guess my idea wasn't such a good one!
I'm not sure exactly what's going on with the AI passing each other. But, I have some theories. I believe that when you set the AI at 93%, every driver is 93% and somehow they "know" that they won't be able to get around the driver in front of them because the driver in front of him is exactly like him performance wise. I'm sure Stefano and Aris would say I'm completely wrong here and I probably am. How the heck would I know that?
However, I am fortunate to be playing on PC and using a 3rd Party launcher called "Content Manager" and I'm able to set a range of AI skill. For example, if I wanted to race AI at 92%, I would probably set my high and low AI percentages to 94% and 90% or 93% & 90%. I don't tend to have nearly the problems that I hear from others with the AI. It's like a 94% guy is coming up on a 92% guy and he "knows" he can overtake the guy who is 2% below him, skill wise.
For all I know, maybe that's exactly how the Kunos AI works even using their base launcher which only allows us to select a single percentage difficulty. I know my anecdotal evidence doesn't mean crap...and I'm not saying that I don't experience any issues at all because that's not true. It just seems like I experience a lot less than others do. It might have a lot to do with how I've switched to Track Days exclusively and every AI driver is in a different vehicle.
You're right. The vast majority of the AI's crazy behavior is in slower situations. At least, that's what I've experienced. I've also been three wide with AI drivers too. The best move I saw them do was on Monza 66: Two really fast super/hyper cars were hauling toward one of those big banked turns and there was a slower car, maybe like BMW M3 or something, driving right in the middle of the track as it was approaching the big banked turn. The two trailing super cars made split decisions to pass the slower car, one going high and the other going low, passing the slower car perfectly, just the way you would want them to behave.
I was impressed because I was afraid they might slow down because of the big banked turn, but they didn't and they also followed their own plan, one going high the other low, rather than both of them going low or high together without any hesitation. That particular Track Day session had some pretty awesome AI driving and I freakin' didn't save the replay file...I wanted to make a little video showing the perfect AI behavior in many different scenarios. There were a few stupid things that I saw that session, but I did a ton of laps and was overall very impressed.
Addressing your edit...I'm not sure I fully understand your question. Are you saying you would like to have multi class driving online against real people? If that's what you meant, I believe it should be easily available. I don't know squat about console version online stuff. On PC we run our own servers and the server host picks and chooses which cars he wants available, I believe. Maybe once Private Lobbies come you'll be able to do that? if that's what you meant.