use bids, not negative auto targets.
you want to end up here:
Ad Group A / Auto Target A / $0.42
Ad Group B / Auto Target B / $0.49
Ad Group C / Auto Target C / $0.72
Ad Group D / Auto Target D / $0.37
Ad Group All / Auto Target All / $0.15
Anything good percolates up from "All", target it in a new Ad Group / Auto Target combo, raise it's bid above the $0.15.
Think of it like people - they all start off equal, pull the better performers out of the group, deal with them individually. Depending on your overall size, you'll figure out when to stop yanking from the general population. But ideally, as you lift more out of "All", it empties out. If your size permits it, keep doing that until everything has it's own gas pedal, leaving the "All" really an empty bottom feeder (your datafeed guy will mess up your adwords_labels or adwords_grouping or some other targeting mechanism's data, and you'll still have your "All" catchall there to keep her flowing.