I don't think it was PEDs alone. The game was so skewed in favor of pitching by 1968, the MLB incorporated several rules changes to balance things out again. The DH was introduced in the AL (the weaker hitting league at the time,) the mount was lowered to 10-inches, and the strike zone was made smaller. I'd like to think that pitchers have also gotten a lot better since the 70s...they're more athletic and also smarter than ever. Look at that Trevor Bauer kid the D'Backs have and Aroldis Chapman with his 105mph fastball...