BP, what you're not realizing is this:
If the Cubs and Astros lose 100 Runs to their RD, they'd still project to finish over .500. If the Reds add 100 Runs to their RD, they'd still project to finish under .500 (and would be 50+ Runs short of doing so).
But really, I think the difference in our thought process on this is that I don't give the Reds bonus points for projecting a sub-.500 record regardless of what other teams did or didn't do to their own squads.
BTW, per 200 IP the difference between Eric Milton and Cory Lidle is about 10 Runs. That's the kind of improvement you're looking at when swapping a below-average pitcher for another below-average pitcher. And when you're talking about that kind of incremental improvment, it's easy to eat it away if just one pitcher underperforms slightly versus 2004.