Hardy did a fantastic job with what he was given; I just wish that they had fleshed out the character's philosophy the same way they did with Ras in BB.
There are lines sprinkled throughout the film that tease at Bane's way of thinking, but they are never given much depth, which I think is a true shame.
For example, he calls himself "necessary evil" - very interesting idea, never expanded upon.
He also says that "people of their stature deserve to witness the next era of Western civilization", and when Pavel tells him that the bomb will go off after the 5 month period, Bane says, "for the sake of your children Dr. Pavel, I hope it does".
There is somewhat of an Old Testament, quasi-messianic dimension that is hinted at with Bane that we never get to see explored. That would have taken TDKR to a whole other level.