So what I had thought was the fault of the lens at the end of this post was actually more the body from my very rough testing of shooting 5D MkII vs 50D in my backyard. The 5D2 just has a lot better contrast and color vibrance straight from the camera, which I would guess is attributed to its larger full-frame sensor.
This is a bit disappointing to me as now I’m less inclined to bring my 50D around, but it’s still a pretty good backup body and I can still use it for its reach. Oh wellllll….