I think you have to consider that when you have a great pitcher on the mound, he faces every batter, while in the game. That is an enormous value. A great batter might get 3-5 chances, buy he can also be pitched around.
I know you are talking about all batters vs all pitchers, so PAs for the offense are in general close to PAs against, so it seems "equal," but I feel having great pitchers, because the face all batters, seem to matter more.
Of course, offense matters, and it matters, a lot, but when we have Crochet on the mound, I'm not worried about the opps O.