I think the current rotation is fine. But I dont think everyone can finish the season in the rotation and the innings that they will have thrown will all be more than ever in their career except Gibby.
Btw, Kremer has a 3.5 ERA since May 1. If that is your no.4 or 5 guy, the rotation is okay.
I would love to add a nails bullpen guy. And if we somehow could pry Goldschmidt from the Cards, Id really like our lineup a lot better.