Actually, it took my 20th viewing to notice that loophole. When Batman is in the prison, his helper/warden is telling him how a child escaped, and how we assume that child is Bane. In the same scene, I believe, he mentions that Bane was beaten by the prisoners and how the mask "controls the pain". Well, if supposedly we are led to believe a child escaped, and the child is Bane... how the **** did the adult Bane get beaten by prisoners to the point of needing a pain-controlling mask?
As for Bane being dispatched quickly, I also felt that to be a bit cheap. He'd been built up all through the film as this combination of cerebral anarchy/socialism and physical power. And as soon as Talia reveals herself as the child, Catwoman blows Bane literally out of the film with the Batcycle's guns. Seems like a rude and unfitting end to a guy who was built up all film as "the baddie".