I have tried making this point before and am surprised you still hear the every day argument. Every play is primarily batter vs. pitcher. So a starting pitcher that pitches 7 innings is in on 39% of the plays (7 / 18), versus the hitter at 5.5% of the plays (1 / 18)
And yet, he only effects the outcome of 30 or so games. And really, probably less than that, because his offense sometimes totally loses or wins games regardless of how he pitches. At best, he can help them in 35 games. A hitter? 162 games. You totally ignore that part in your calculations.