If we look at one of Jenson Button's weaknesses like qualifying, hes probably equal to Rosberg in that area. In any other area Button is much better and a lot more complete, which is why he wins races and gives top drivers a hard time. Rosberg has big flaws in his ability that will give him a lot of problems if he gets his hands on a race winning car. His overtaking skills are questionable and hes horrible at defending. He might destroy Schumacher over one lap but things are a lot closer in the races.
Actually it was Matra, March, Tyrrell, BAT, BAR, Honda, Brawn and then Mercedes, what it will be next who knows