Hopefully EA will sort this soon in an update, until then I'll stick to the cars and tracks which feel right (I have given up on career mode with the clio-at-fuji-esque AI as they are too ridiculous for words).
I have come to feel better about the AI over the last couple of days.
Here's the problem: entering a relatively short race, on a track you're not that familiar with, in a car you haven't driven before.
That's Career mode!
I've mostly been driving in Quick Race. There you can set the AI on Hard, so that it drives more or less as fast as you - no constant rear-ending the AI. Set the race for a longer time - so you don't have to bang your way past the AI to win. Drive a track you know well - so that you can drive at the limit & not have the AI rear-ending
you. Drive a car you know well - so that you can drive at speed & under control all the time.
Under these circumstances, the AI actually seems pretty good - aggressive, but not unreasonable - much, much more interesting than GT's. You would never, IRL, jump into a unknown car on an unknown track & have a decent (& collision free) race. The problem is, to progress through Career mode you are constantly put into a position where you have to do this, and, not surprisingly, total mayhem results.
The most impressive example of this so far, is the Nordschliefe/Veyron Invitational Race. Yup, someone's lending you a
Veyron to drive for the very first time, in a
race on the
RING!
The most reasonable strategy for this game seems to be: practice time trial laps in QR, until you know the car & track well, then race the AI on Hard in QR. Play Career mode just to progress through the tiers. Get online against other drivers who know what they're doing.