There is little doubt the return for the Harden trade is likely to not be as good as just keeping James Harden. However, trading Harden had just as much to do with economics as it did with on court performance. It is unfortunate that the latest CBA is so punishing with the luxury tax. The punishing luxury tax causes smaller market teams more problems than the large markets. The Lakers's TV contract is worth $250 million annually. With TV money alone, the Lakers can carry a huge luxury tax bill. The Thunder's TV contract is about $15 million. That difference makes it difficult to pay a large luxury tax bill, which the Thunder would have been paying had the team not traded Harden.
This article from Grantland's excellent Zach Lowe breaks it down further:
Thunderball. I highly recommend reading everything Zach Lowe writes. He does a fantastic job breaking anything and everything NBA down.
However, it should also be said that the Thunder were still incredibly good on both sides of the ball last year. The talk of the Thunder being down stems completely from Russell Westbrook's injury during last season's playoffs. There is not a single team in the NBA, and that includes the Miami Heat, that could recover, especially that late in the season, from a devastating injury to the team's second best player and a Top 10 player in the NBA.
This is still a very good Thunder team, a team with the second best player in the world and another top 10 player. Both Durant and Westbrook do need to continue improving and that should happen as both get older. Durant and Westbrook are just 25 and 24 years old. It certainly feels like both are older because both have been featured so prominently within the NBA for a number of years already. Serge Ibaka is also just 24 and has shown very nice improvements each year.
The Thunder also need their role players to step up their game. That has been a big weakness in the close games. The team does not necessarily need huge performances. Stepping up to the plate and hitting a single or double would be great, instead of striking out on obvious strikes.