I am also a bit put off by the number of cars that exhibit lift off oversteer
I dont think that what you are suffering with, is just a case of lift off oversteer, but also the weight of the car shifting. Myself and
@ImaRobot have been hashing this out for a couple of weeks now on the FM.net forums. And testing cars that people say are not drivable in game due to lift off oversteer, such as the 370z
Driving stock on a default xbox controller with abs/stm/tcs turned off:
Driving stock with my Logitech G920 wheel set to 900°, with abs/stm/tcs turned off, but using a combination of weight shifting/braking feints/lift off to drift it:
And what we have seen, is the fact that most people are either reacting way to slowly when the rear does brake loose. Braking way too hard and too late, which is shifting all the weight forward and off the rear tires (how to initiate a braking feint drift). Driving way to fast into a corner, as they do not get a decent representation of the speed they are attempting to enter at. Some are saying that 70MPH+ feels like 30MPH-. Or they are coasting for the entire corner. I don't know about you, but with regards to the last item in that list. I was taught never to be off the throttle by my driving instructor when taking a corner at speed, such as you would find on a 60mph A-road here in the UK. Even more so if you was coming off a steep downhill gradient, such as can be found around the Yorkshire Moors, and in the Lincolnshire Wolds. Let alone what can be found in Scotland. That isn't to say you should be accelerating however, just keeping your speed, which in turn keeps the car balanced through the corner.
In any sim based racing game that I play, I always mess around with weight shifting as a way to enter a drift. I do this in Forza, I also do it in Assetto Corsa, Rfactor and Iracing. I do this so I can learn how the cars handle and react, and how to stop unwanted behavior from happening during a race. A lot of people seem to be initiating an inertia drift without meaning too in Forza, and I have seen people inadvertently do it in the other games I have listed also. And it is all to easy to do.
With regards to lift off oversteer in real life, different cars are effected by it to different degrees. Some, such as MR's and FF's can be very prone to it. FR's, it all depends on how the car maker has set it up. But all cars will suffer with lift off oversteer at some point and to some degree, even those renowned for been highly stable. There is also another fact to consider here, and it comes down to the driver aids.
The vast majority of cars been built in the last 10 years, will have driver aids to some degree in them. Such as STM, which helps to reduce the likely hood of a spin. The cars are designed around them now, and they are more advanced than they was a decade ago. Especially with cars like the Mclaren P1, which are designed to be driven with those driver aids engaged. Even at speed on a track, as the system used can learn and make you slightly faster. If you asked a Mclaren engineer how to disable those systems in that car, I bet they would think you was insane. With those aids turned off, the car would be a major handful. Just like it is in Forza, and just like it is in Assetto Corsa. Regardless of the levels of mechanical grip it has. With those aids turned off in a video game, we have to be more mindful of all our inputs. With those aids turned on in a video game, we can just mash the throttle, and slam the car left/right to a point. And it will stay vastly more in control than without them. Even the F458 is designed not to have those systems turned off in real life, and the newer Lotus Exige S is also the same. We all know how much more difficult those last 2 cars are to control in Forza with those driver aids turned off, and again, it is the same story in Assetto Corsa. Which also has those 2 cars in it. Even something like a 3rd Ford Focus Zetec has some driver aids built in, and they lull us all into a false sense a security. And they reduce undesirable effects when our driving is less than good. In racing games, if you are like me, you will turn all those aids off. Including ABS.
I used to have a Fiat Grande Punto Sporting, which had a 1.9litre turbo charged diesel engine. It had 130BHP and 206lb feet of torque, and I once turned off the stability management. It didn't take too long before the rear end stepped out off throttle. I wasn't going all that fast (around 40mph), and luckily I was in a front wheel drive car. So a little throttle pulled it back into shape. If I was in an MR, or even an FR and did the same thing. I am not sure I would have been able to correct the behavior (no experience driving those layouts in the real world). I was also on private land with plenty of space, so I didn't put anyone at risk. I certainly am not endorsing people to try it on a public highway, as that would be crazy. But it was something to learn, and something I would likely of never experienced had I not turned off the stability management in my car. The abarth Punto (closest car to my old grande punto sporting) in FM5/FM6/FH2, exhibits the exact same behavior off throttle with the Driver aids turned off.
There is also one more thing to consider. In the real world we have a lot more sensory information, and because of that extra information. We can and do drive differently. In a video game, we are only reacting to sights and sounds. Some, like me and you, have a wheel. So we do get a little additional feedback, but it is not the same as driving a real car. Then there is also our built in survival instinct to consider. In the real world, we have a fear that out actions my cause. We are worried about crashing a car, about hurting ourselves or someone else. Things we do not experience in a video game. The only thing that we have that comes from the real world, is an adrenaline rush, which we will all feel when having a close race in a game. Or in a tight match in COD/Battlefield, and so on. That lack of fear means will will push harder in a game than we would for real, and that fear is not keeping us in check. I certainly know I wouldn't drive as fast on a track in real life, as I do in Forza or other racing games. Because I wouldn't want to end up in hospital or worse.
As for Forza Motorsport 6's physics, and comparison to other racing games. I find that FM6, and even FM5 before it. Are getting very close to what I have experienced on the PC racing sims around. They are not 100% there yet, but no sim currently commercially available is. And I doubt they will ever be, based on just how much information we lose from the real world to a video game. FM6 is certainly getting close to the likes of Assetto Corsa and Iracing.
Anyway, that is my opinion on the matter. And in regards to the physics of FM6 compared to the other sim based track racers I play.