The sensitivity is really pretty subjective too. The +2/-1 that I mentioned is how much I like it to vary to suit my driving style and my enjoyment of the car at the limits. In reality other factors can alter the balance to the point of absolutely swamping the setup values, in which case you just accept it and adjust to drive accordingly on the day. Driving style can trump everything.
At November's interstate challenge meet I was having major front tyre problems, basically bugger all front grip. This got to the point in the last session where a couple of my Vic mates following me said I was going through turn 2 at almost full positive lock (full understeer

). It was definitely not the way I wanted the car to feel but it was still running mid 13s with a flat motor and gear selection problems (again

)