http://www.hardballtimes.com/winshares/index.php
That'll give you a look at the statistic and player numbers for each team.
Keep in mind that it's not an inaccurate measure of contribution just because you don't want to believe that it's accurate. The very same metric will show you that Derrek Lee and Albert Pujols are 1st and 2nd respectively in all of baseball in team contribution.
In fact, you won't be able to find a meaningful performance measurement that doesn't demonstrate that Dunn's contributed more Runs to the Reds than any other player on the team.
Oh, and a couple quick questions:
1. If BA with RISP is actually what drives contribution, then why does Sean Casey have pretty much identical RISP RBI numbers while Casey has a nearly 20 more AB with RISP and a RISP BA advantage of over 80 points?
2. Why does Adam Dunn have more RBI with Runners On than Casey even though Casey has over 30 more AB in those situations and a Batting Average about 80 points higher than Dunn?
3. Does base hit type matter or are all base hits created equal?
All valid questions considering your position and all need to be carefully considered. I think you'll find that the right answers will give you a bit more direction in really understanding how players are able to contribute to their ballclubs without needing a .300 Batting Average.