Be careful which way you draw the causal arrow. Those performances aren't happening as a result of the Reds losing games. Rather the Reds lost games when players performed at that level -- along with a number of other factors (pitching and defense).
We know that in a given game, no one players' performance counts for more than another's (scaled to PA) and this reflects that. As a team, the Reds lose when they struggle to score runs and they win when they score a lot of runs. The combination of players who struggle or succeed isn't really all that important compared simply to how many players struggled or succeed.
That Bruce's split is so extreme simply shows that his struggles and success were most strongly correlated with the struggles and success of his teammates. Not that his struggles and success were particularly influential. There's really nothing here which suggests that the team struggled because of Bruce, that Bruce struggled because of his teammates, or if there is any meaningful causal relationship at all.
Rather than looking for some causal relationship between Bruce and his teammates, I think the more likely explanation is a strong correlation of offensive performance and opposing pitcher quality. Facing a good pitcher, everybody tends to perform worse. Facing poor pitchers, everybody tends to perform better.
In this model, one possible explanation for Bruce's extreme split is that his great talent lets him destroy bad pitching but his still-in-development plate approach makes him particularly susceptible to good pitching. Additionally, given the way OPS is calculated, players whose OPS is disproportionately comprised of SLG will be more strongly impacted by this effect. So guys who tee off on bad pitching are likely to experience the biggest splits.
Code:
OPSloss OPSwin Split Var
Jay Bruce .566 1.019 .453 -.196
Laynce Nix .543 .851 .308 -.051
Joey Votto .803 1.109 .306 -.049
Drew Stubbs .582 .887 .305 -.048
Scott Rolen .718 1.001 .283 -.026
Jonny Gomes .675 .925 .250 .007
Miguel Cairo .562 .793 .231 .026
Orlando Cabrera .602 .819 .217 .040
Ryan Hanigan .633 .846 .213 .044
Brandon Phillip .641 .853 .212 .045
Paul Janish .516 .728 .212 .045
Ramon Hernandez .638 .836 .198 .059
Corky Miller .487 .646 .159 .098
Average .613 .870 .257 .000
Var is the difference between the average split and the player's split. Check it out. See a pattern? Big slugging guys at the top, small slugging guys at the bottom. Put simply, the bigger they are, the harder they fall. I think you'll find that SLG or ISO accounts for a good amount of what you're seeing here.