For each pitcher from 1993-2011 with at least 5,000 Batters Faced, I've added up the average growth in run expectancy per NIBB. The average increase in RE for an NIBB over that period was .323 runs, which jives with Tango's findings here. There were 175 pitchers in the sample, with a standard deviation of .013.
The pitcher who gave up the least damaging change in RunEx with at least 5,000 BFP was Rick Reed at .258 RE/NIBB, a full .065 better than the league in that time. Reed scores just ahead of Gregg Maddux at #2 with a change of RE .041 better than the league. – James Gentile