For me, Bale's performance, not how Connor was written, but his performance, and Sam Worthington's, were the best part of Salvation and good enough I still watch it and accept it in the franchise.
I do think that it suffered from the overall writing and storyline, but also for the fact that it built off of T3's established alternate timeline. It's the trouble with time travel movies, but for things to work, the events of T1 and T2 both would ultimately lead to the future Kyle went back from, but instead, T3 took the route that it would not be the case, that the path of the future would change with the events of T2 and John would become a scared loner living off the grid and hating himself, which is ultimately where Bale's Connor would evolve from, and instead of being a skilled leader, he became treated like Neo in the Matrix.