Ok, got it. I had adjusted the small spring tension adjustment screws before, but only on the side giving me trouble. I though it was just somehow changing the distance of the brake pad from the brake arm, moving it closer or farther from the rim (and doing this independently of the opposite arm)... I realize now that this is so very much not the case. Thanks to you guys cluing me in to the fact that it is actually adjusting the spring tension, therefore it stands to reason that adjusting one side will affect the other. I hadn't realized this. I chucked the wheel on just now and adjusted both sides and it evened out perfectly.

Turns out it was a noob question after all. Pacifica, I may still have a look at the washer stack just to see if I can really get it tuned up perfectly. Anyway, thanks everyone for your help.