Four is Too Many
The Lakers need only look to their own history to see this: four stars is just too many for an NBA team, almost without fail. That goes double for importing two new stars in an offseason to join two existing stars. The 2004 Lakers were expected to dominate after adding Karl Malone and Gary Payton to Kobe and Shaquille O'Neal, and while they played very well at times, they were dominated in the NBA Finals by a Detroit Pistons team that was practically devoid of stars - at least at the time.
Adding Steve Nash and Dwight Howard to Kobe and Pau Gasol before the season was a recipe for disaster. Having four guys capable of scoring 20 points is great on paper, until you realize that there's only one basketball on the floor at a time.