Thanks for making this thread, I find it an interesting topic.
Here is a metric of dominance which records the percentage of 1-2s and 1-DNFs over the season. I've called it 'Race Supremacy' because of the implication that no other car is able to beat the car in that race.
Including 1-DNFs may not be exactly to some people's tastes, but I think it makes more sense when you consider the inverse metric (i.e. 1-this_metric), which records the number of races where another car is able to beat our car of interest - the higher the inverse metric the lower you would assess the dominance of such a car.
Observations:
The "Race Supremacy" metric also assumes that if there is driver disparity (e.g. only vettel being able to 'switch on' the RB7), then this penalises the car. Therefore, according to this metric much of Red Bull's domination in 2011 appears to belong itself to the man-and-machine combination: that it is Vettel+RB7 that dominates, not just the RB7 itself.
This again shows that the MP4/4 is the most dominant car, but the W05 is a real rival to it!