I believe a third superstar can be close to fully utilized, more so than Minstrel and ESPN HOF are projecting above. First off, players don’t play the entire game, they take breaks and have foul trouble, but with 3 studs in there you can leave two of them in for almost the entire game. Hypothetically, if you played exactly two of them at all times each player would still play 32mpg. There will be long extended minutes where all three of them are not in the game together; teams like the ’96 Bulls had to make do with long stretches where only MJ or only Pippen were in the game. The opponents often had runs during these stretches, but the Bulls would be deadly during the final 6 minutes when they were able to play all of their stars together and close out games.
The Miami trio also will benefit from individually exerting less effort on offense while on the floor together. There are times this year when LeBron or Wade would have to initiate the entire offense for many possessions in a row, 10 or more. But in Miami those guys can hold back some energy for the end of the game, or for defense; whereas last year they had to fight so hard to keep their teams in the game during the 2nd and 3rd quarters. Wade was a super sub on the Olympic team that came in and got steals leading to high percentage fast breaks, now Wade can play that type of defense at times and not worry about his team being decimated later on if he can’t carry the majority of the offense. LeBron was a good defender last year, but now he could focus entirely on shutting down a player like Kobe.
As others have said these three chose to play together. They want to be a smaller piece of a team, but be part of an elite team. With that attitude I expect them to find effective new ways to contribute compared to being the lone centerpiece of a team.