You're right that the Rangers had huge holes at a lot of other positions and it killed their overall wins...but an uberstat like PCA should SEE that (and it does...the Rangers' pitching staff as an entire UNIT was very close to the margin and their fielding units weren't much better). You can track supermarginal performance easily enough. The question is how do you decide what that supermarginal talent is worth. My first guess was to place the supermargin at the exact opposite side of the value spectrum from the real margin and track supermarginal wins linearly up (on top of normal marginal wins) in the same way that I'd track sub-marginal wins linearly down from zero. Maybe that's not right, but it's better to guess that than to ignore the supermargin altogether as all other metrics do.