Re progressive leagues:
Overall offense is influenced by teams that have a lack of IP and/or owners who aren't exactly trying their hardest (I'm not using the "T" word, I'm just sayin').
It would make more sense to look at the stats of pitchers belonging to owners who are managing their staffs appropriately (i.e., not sending their pitchers into games tired, or giving them pitch counts that are unreasonably high).
If these pitchers are putting up noticeably worse stats than they did in real life, then there might be a problem...