You realize that if he takes less shots, his teammates need to take more shots and their respective TS's drop and TOV's rise, right? You seem to not grasp this.
No, I actually do grasp this concept, but it's not as extreme as you make it out to be. But if Harden is taking another 3-5% of the shots, there's no reason to expect
his TS to go down 13%. And if Durant's usage goes up a couple of percentage points, there's no reason to expect his TS to go down at all. The key ingredient in all of this that seems to elude you is that
both of these guys are much, much better shooters than Westbrook. Also, a key component of usage is turnovers. Westbrook turns the ball over less and suddenly, his usage goes down a bit, too. So, if he kicks the ball out to an open guy on the wing/corner 3 more when he drives, his usage goes down, assists go up, TS% goes up AND I bet some of the role players' fg% goes up. Some of those guys aren't exactly Steve Kerr but they can hit an open shot (they're not exactly Rondo, either). Sefo has a 53% efg% (shoots over 40% from beyond 3) & Cook is a former 3-point shootout winner. These guys can make open jumpshots and are much more likely to than RWB to make a layup with 2 7-footers converging on him as well as his own defender.
The part with expecting him to shoot better because his teammate shot high %'s makes no sense.
I don't expect him to shoot better because his teammates shoot high %s. That would be idiotic. I expect him to shoot less. When you drive the lane and 3 guys converge on you, kick it out. Don't try and force up a lay-up that has no shot at going in.
You're not Dwyane Wade; the refs are not going to bail you out (yet).
Bottom line: There aren't a whole lot of guys out there that are better scorers in the NBA than RWB. Ideally, you'd surround Durant (and Harden) with a younger PG who can shoot as well as create for others (like Ty Lawson, maybe) and replace Perkins with a big man who can give you some easy points by scoring in the post. The first exists. The second... not so much. Those guys are so rare these days that OKC will likely never have the opportunity to draft one and are positioned geographically to not be a hugely desired landing spot for FAs. But since the likelihood of replacing RWB with that combination is next to nill, the next best thing would be for him to shoot less and turn the ball over less. Seriously, kicking the ball out 2 to 4 more times a game would increase efficiency all around. His usage would drop, his missed shots (mostly blocks) would drop, his role players would get an extra shot or two.
The real bottom line: I'm not OKC's coach or GM and neither are you, so none of our opinions mean diddly squat in the long run. It just pains me every time I see him having a 2-for-17 night and see him keep doing the same thing over and over when he has two other excellent offensive options available as well as a few guys that can hit a shot.