I see Adam Dunn as a perfect example of why a 5x5 scoring system is simply inadequate. Keep the traditional 5 - BA, HR, RBI, R, SB - and add OBP & SLG or OPS. Now all those walks, 2Bs, and 3Bs have some value and the low BA still hurts.
If Adam Dunn ends up in the 50 solo-HR club, is that really his fault? If every batter in a lineup were Adam Dunn, what would the probability be that he hits a solo HR, 2-R HR, 3-R HR, or a GS? I'm guessing that he'd hit multi-R homers more than most hitters in a similar analysis. Adam Dunn is a guy I'd take in my lineup any time.