Most probably parts on bench would help. As I know I have first hand experience of cars with completly burned out VC's driving just fine in normal road driving. When I bought mine it was winter and when pulling off from traffic light it would spin rear wheels endlessly and understeer cathatrophically spinning fronts if you applied any throttle whatsoever in corner entry phase but it still drove just fine and pulled up to 230km/h with no problems.

It should be epicyclical diff making the torque split and VC only providing LSD action. If it is not then I am really feeling stupid and don't make any sense of it all.