Tyre wear is definitely broken at the moment. Been attempting to do the Tokyo Expressway grind for which I have been using Sports Medium tyres (Tokyo Expressway historically has had low tyre degredation).
I'm able to get within a few tenths of my fastest lap with the wear indicators very red. Grip was fine, felt like maybe 30% wear pre-update. But as soon as the tyres went fully red on the indicators, the next lap I dropped around 16 seconds in pace and the car simply refused to turn. The cliff was immensely steep, instant even.
Really hope that they fix this, even going back to the pre-update system. Same goes for the sensitivity for mechanical damage. The slightest tap on a wall that wouldn't even trigger a penalty will now give you front aero & suspension damage.
Because of these factors, I am currently unable to efficiently credit grind as most decently paying events feature tyre wear. It also would seem that the A.I. are unaffected from what I can tell. Really hope these get either reverted or fixed before the McLaren MP4-4 becomes sold out.