No, not really. Do the math--replacing Barnes with KD is +10 in shots/game based on last year's numbers. Having each of the top 6 take just ONE less shot per game and that's down to +4.
Add to that the fewer minutes played due to the likelihood of blowouts and it's not going to be a huge issue.
I'm not arguing with your math, but I just dont think it works that way. Because its not exactly the mentality of 'at the end of the season will I have the 1,400 shots I expect', its changing from shooting and touching the ball at the rate that you are accustomed to. Its getting each member of your top 5 lineup to accept a certain role to make that top 5 work and accept that less of the offense is going to run through them. In your top 5 lineup the FGA per 36 for that 5th wheel cant get any lower, not because the coach demands to get that guy a specific number of touches, but because that guy is forced to take a specific number of shots to keep opposing defenses honest & bail the team out when the shot clock is winding down.
Simply putting it as less shots might be over simplifying it. Last year Durant averaged (these are all per 36) 19.3 FGA, 5 assists and 3.5 turnovers, so thats 27.8 plays per game where he was the guy, he either got to shoot it, make something happen to get an assist or he screwed up and turned it over. Barnes meanwhile averaged 11.2 FGA, 2 assists and 1 turnover or 14.3 plays, which really highlights that he was a 'stand here and shoot it if we give it to you' guy, and this is 13.5 fewer 'that was possession' plays than Durant. I'm sticking with my theory that your 5th wheel simply has to touch it that much, so now we are asking all top 4 guys to accept 3 less plays like that per game and all of them are going to have to play differently as well.
With Curry for instance, he is going to have to get used to playing more off of the ball, holding it less, shooting less and deferring to Durant at times. Green will have to primarily play down low, wont get as many touches and certainly wont be anywhere need the 7 assists per he had. Thompson isnt going to get to operate with the ball much at all, and he is probably going to be the most impacted by taking less shots. Durant certainly played nice with Westbrook so the deferring to Curry might not be a problem, but his game will have to change and he is going to shoot less.
I'm not completely doom and gloom about this but there are going to be some challenges thats all. These are the issues that arent problems for fantasy teams but are problems for real teams. Like look at OKC, I guess Ibaka was upset this year because he was promised that he was going to be featured more in the offense and thats Ibaka. There are just some inflated egos in the NBA.