I think I figured out why the rain seems impossible to drive in!

Try the Camaro at Lime Rock, that's the main one the AI was having massive issues with, it could be a track problem.

Also, the sensitivity doesn't seem to matter, it still spins as soon as I hit the throttle.

 

Lime Rock with what choice of chicane?
What pedal set are you using?

 

No chicanes, and I'm using a 100% vanilla G25.

 

Okay, after playing around for the last ~30 minutes, I'm starting to get the hang of it. Having the throttle indicator has done it for me, I think, it makes it a lot easier to see where my throttle is and if I'm putting too much power down.

I still believe that it is exaggerated, but I suppose it isn't impossible. In the Camaro I've started shifting up around the green lights rather than at the top of the rev range, that's helping a lot.

 

Didn't see any Camaro AI misbehavior in a 10 lap rain race other than the non-leaders coming in for a tire change on the last lap because it had quit raining (track was still wet).

My pedals are G25 with stiffened springs (GTEye? Can't remember) & a Nixim brake rubber & Bodnar cables, throttle and brake sensitivity at 75%. The AI are lapping at 57s-58s on 100 difficulty, 50% aggression. I'm usually lapping in the 1:01s, best was 1:00, with the ISI default setup (with rain tires) by shortshifting when the initial green light appears or just before. Able to achieve full throttle down the front straight, but am cautious on the back straight due to a couple bumps as you cross the crown in the road. You might try starting in 2nd gear instead of 1st. Remember that rain amplifies mistakes.

Clio AI will rollover often if you don't use the uphill chicane. They'll still roll occasionally on the diving turn.

[Edit] Hah, I was interrupted by a phone call while typing, so didn't see your response. Good to see you're finding the groove!

 

Playing with the Camaro on Mills now, along with a couple of other cars. Am I right in assuming that both the Formula ISI and Formula 2 need to be updated to work properly in the rain?

Other than that, I think the exaggerations are mainly with the massive understeer (since when can a modern GT3 not turn almost any corner at 15-20MPH?) and how little throttle it takes to lose grip. I've changed my sensitivity all way down to 30%.

 

I have the G25 with GTEye Brake Spring and "in the post" Throttle Spring plus Bodnar Cable, I find the Brake alright at 100% but may tweak it a bit when the new parts arrive.
Running in the wet is the perfect way to get the Pedals setup for personal taste as those very slight pressures/touches can mean a world of difference, get that area sorted and running in the Dry becomes that much better too.

 

With the right tyres, VEC are not using URD wet weather compounds, but our own

 

Aha, didn't know that.

I just gave the Camaro a spin at Lime Rock park uphill chicane in 100% rain. Can't say I notice any strange behaviour. The thing that does stand out to me is that the car has a LOT of torque, so you really have to be gentle with the throttle on corner exit.

SeriousSpy, take a look at the "technique" section in the link below, maybe it helps your understanding of the car:
http://rfactor.net/web/rf2/cars/chevrolet-camaro/

It can also help to make some adjustments to the car's setup for rain. You can usually lower the front and rear ARB's a bit to compensate for the lower corner G's, as well as lowering the camber a bit. Perhaps a higher rear wing angle as well. Brakebias a little to the rear (although the Camaro's default setup already has the bias pretty far to the rear). That should get you started.