Wow, you mean they win better with both guys than with just one? Who would have thunk it?
The question is would the team be better, especially in the playoffs, with a player like Rondo who would allow Durant to be the dominant scorer instead of he and Westbrook fighting for the position as they have in the past within the confines of Brooks' high school offense.
Did you watch last year's playoffs, when Durant was slumping (relative to his standards) and Westbrook was, by far, their best player? Did you watch the 2013 playoffs when the Thunder sputtered when Westbrook went out with injury?
The answer to your question is an obvious "absolutely not." The idea that these guys are "fighting" to be the alpha male is as dated as the Honeymooners. If anything, Westbrook has deferred to a fault in close games this season by force-feeding a not-completely-healthy KD.
The Thunder need a new coach.
Also as much credit as Presti deserves for putting together Westbrook / Durant / Ibaka in the first place, he hasn't done a very good job putting together a supporting cast for the team since then. That has put too much of a burden on the stars to make up the difference.
Yeah, I've gotten on Presti for his roster construction this season... but he pulled off arguably the best trade of the deadline, if not the season, last Thursday. This is now the deepest Thunder team ever; OKC has never once had this many weapons. All they need is KD to return without issue.