In my opinion yes, that dor would be a hindrence in the fact that you only have to move the wheel a couple of degrees to have a large impact in steering input.
For example if it were set to a dor of 900 degrees, a quarter turn on the wheel doesnt do much to the steering in game.
It is similar to real life.
Therfore it makes countersteering a slide easier beacuse there is less chance of overcorrecting oversteeing in the heat of the moment.
I personally have found 720 works well for me.
I like to tune myself.
Differential is one of the most overlooked factors in tuning.
I think it is one of the most important if you drive unassisted, eg: no traction control.
It acts like a lsd. Eg:
With high front accel diff, when exiting a bend both tyres spin at the same speed resulting in oversteer.
With low front accel diff, one rear tyre rotates between 10-30mph slower than the other rear tyre resulting in a great corner exit with minimal spinning.
Differential Acceleration:
Turn this down to around 40 in high powered rwd cars as a starting point.
You can go lower but you need to find the sweet spot where turn in for certain bends isnt affected.
This is different for every car.
Done correctly you will have sharp and direct turn in, with minimal loss of traction for rwd drive cars on the corner exit.
Differential Deccelration:
Generally this has the effect if turned to low of unexpected/sudden oversteer when heavy braking or sudden downshifting causing the car to oversteer when approaching bends at speed.
Lowering this setting gives your car a better corner entry turn in, but set too low and the above happens.
This setting is always best lowered but again finding the sweet spot so corner entry isnt impaired is trial and error.
Again you want to start on 40 and work down from there.
In general my cars normally run between 25-45% accel diff for high powered rwd cars
50-75% for low powered cars eg 100-350 bhp.
Another quick tip when tuning is to bring your telementry up by pressing up on the d-pad when test driving.
Press right on d-pad until tyre pressure and heat is displayed.
You want to aim for between 32-33 psi when tyres are at optimal temp 190-220 degrees c.
If you want more pressure and heat increase the tyre pressure.
If you want less pressure and heat decrease the tyre pressure.
The second thing i do is display the inner/middle/outter tyre pressures in telementry.
You want to achieve an even spread of temp accross the tyre.
To achieve this adjust the camber in small increments.
I Also adjust rear toe-in by upto 5 degrees at max, depending on your car.
In the tuners section there are some excellent guides which go into far more detail than me.
Hope this helps you to minimise your oversteering situations pal.
Ps. The Th8a shifter is awesome. Well worth the money.