[If it isn't already obvious by this thread, massive SPOILERS ahead]

See I didn't see it all that forced. The relationship with Miranda didn't need to be drawn out any more than it was because it really was a spur of the moment situation as she was trying to seduce Bruce to get what she wanted and Bruce was simply in over his head being back in the game after so long, as was brought up over and over by both Alfred and Fox during his reclusive state. No need for it to draw out as any implied "relationship is simply that, implied.

There wasn't any real time to develop a relationship with Blake, given that Bane had already begun his attack well before anyone had known or could have expected, so Bruce had to act on instinct. He didn't have many people he could trust and Blake, right off the bat, showed Bruce he had balls to confront him and was likely trust-worthy, not unlike his complete trust for Gordon. Also given Bruce Wayne's consistent habit throughout all of Batman's history of researching everyone he comes in contact with, it goes without saying that he probably did a bit of snooping on Blake just to be sure. Again, not necessarily needed for the film. And being that Blake proved himself again and again throughout the film only justified that he'd take the reigns of Batman after the "death" of Bruce Wayne.

Bane's introduction and story was the obvious central plot and was delivered well as someone who'd been working behind the scenes for years without a Batman around. I didn't feel rushed throughout the entirety of the film as everything just made sense. Granted I went in knowing all the new characters' original backstories and understanding a lot of the implied instances so maybe I'm more apt to feel that the pacing was done well. To split it into two movies would just be overkill.

edit: a word