I don't believe PED's have been eliminated as yet. I think players who are not using may now be less inclined to use with players starting to believe that the league may finally get its act together with regard to prevention. So I think it is going the right way.
As for the hitting totals, pitching has gone through several phases of prominence and decline in MLB. As has already been pointed out periods of expansion wreck havoc on the quality of pitching, especially starting pitching. Expansion or the lack of same is usually the biggest factor. We have had live baseballs, dead baseballs and differences in mound heights all of which have made contributions one way or the other.
Clearly pitching is resurgent again and that usually really means starting pitching. The difference during this phase of the pendulum swinging back is that we now have fully developed the concept of the relief pitcher as far as it has ever been and certainly farther than it historically ever was. So this time, as starting pitching improves, we now have specialists all over the bullpen. Obviously, we have the closer. However we also have the fireman. We have the matchup guys and we have the guys that are tailored for the innings leading up to the closer.
Some of us probably remember what it meant to bring in somebody other than a guy who was supposed to take the ball through the ninth inning back in the 60's. If your team had to bring some guy in that clearly was not intended to finish the game or that was not your very best bullpen arm, your head was in your hands and your heart was in your throat. "OH no....not the relief pitcher"!!!!! Now its what inning is it and do we bring in our "X" inning pitcher or do we start to go match up or do we need to put out a fire first. "Oh its the 9th inning......closer".
I actually believe that PEDs will not ever be completely eliminated in baseball. I believe that the PA, owners and players will eventually come to terms with PED usage....mainly as a means to get injured players back in the game sooner rather than later. I suspect that eventually you will see baseball crack down hard on use purely for the sake of enhancing performance while at the same time regulating use for purposes of reducing time on the shelf due to injury. I think that will be the trade off...legal usage for recovery from injury for meaningful testing and truly ugly fines and suspensions for performance related usage.