For starters, I want to say that I am not freaking out over the Bane voice. I have taken a step back, and my official stance on the subject is that we have no room to judge just yet. That being said, I have compiled some evidence to figure out why we heard what we heard (or are hearing what we are hearing).
From Wikipedia, a short summary:
Bane was born in the fictional Caribbean Republic of Santa Prisca, in a prison called Peña Dura ("Hard Rock"). His father Edmund Dorrance had been a revolutionary and had escaped Santa Prisca's court system. The corrupt government however decreed that his young son would serve out the man's life sentence, and thus Bane's childhood and early adult life are spent in the amoral penitentiary environment. Though imprisoned, his natural abilities allow him to develop extraordinary skills within the prison's walls. He reads as many books as he can get his hands on, builds up his body in the prison's gym, and learns to fight in the merciless school of prison life. Despite his circumstances, he finds teachers of various sorts during his incarceration, ranging from hardened convicts to an elderly Jesuit priest, under whose tutelage he apparently receives a classical education. Bane murders this priest upon his return to Santa Prisca years later. However, he commits his first murder at the age of eight, stabbing a criminal who wanted to use him to gain information about the prison. During his years in prison, Bane carries a teddy bear he calls Osito (Spanish for "little bear"), who he considers his only friend.[5] It is revealed that Osito has a hole in his back to hold a knife that Bane uses against anyone who bullies him.
Bane ultimately establishes himself as the "king" of Peña Dura prison. The prison's controllers take note and eventually force him to become a test subject for a mysterious drug known as Venom, which had killed all other subjects; the drug is administered by a doctor who bears a passing resemblance to another Batman foe, Dr. Hugo Strange. Later, in Vengeance of Bane II the very same doctor encounters Bane again in Gotham and it can be confirmed that it is not Hugo Strange, who at that point in Batman continuity was a crazed psychologist and not a surgeon. The Peña Dura prison Venom experiment nearly kills Bane at first, but he survives and finds the drug vastly increasing his physical strength, although he needs to take it every 12 hours (via a system of tubes pumped directly into his brain) or he would suffer debilitating side-effects.
The thing is, we've had reports of some of the things mentioned in that summary. We've heard phrases being used like, "mad scientist". We've heard words like, old, raspy, and weak. Did you happen to pay close attention to the last line of that summary?
"....although he needs to take it every 12 hours (via a system of tubes pumped directly into his brain) or he would suffer debilitating side-effects."
Now, i'm not saying I was there when they filmed this or anything, but clearly Bane is wearing a mask that looks like it could implement a few tubes (i.e. the 'skull fingers'). Also, maybe the scene we saw was an early or a very late scene, and Bane is weakened. The side-effects may be taking place at this part.
Moving on, remember the part in that football field video where Bane says something to the effect of, "Why won't you reveal yourself?". Here's another excerpt from Wikipedia.
Aware that a direct assault on Batman would be foolish, Bane instead destroys the walls of Arkham Asylum -- allowing its deranged inmates (including the Joker, Two-Face, the Riddler, the Scarecrow, the Mad Hatter, the Ventriloquist, Firefly, Cavalier, and Victor Zsasz) to escape into Gotham City. Consequently, Batman has to spend the next three months rounding-up the escapees. Having run himself to exhaustion in the process, Batman returns to Wayne Manor after completing this mission—where Bane ambushes him (having previously determined his secret identity). Bane attacks Batman in the Batcave, defeats him, and delivers the final blow: breaking Batman's back, leaving him a paraplegic. Bane thus becomes the only man to have "Broken the Bat".
Keep in mind that most of the above mentioned villains are not present in the Nolan-verse, so this could mean only The Scarecrow would be released. Maybe Two-Face, but that's a bit of a stretch. Anyway, if you go to the Wikipedia article for Bane, the article clearly illustrates that Bane knew Batman's identity. As a sidenote, the Wikipedia article for Ra's al Ghul also says that Liam Neeson is reprising his role in TDKR, but that's not confirmed yet.
Now...here is a special excerpt. Remember how Bane supposedly mentioned an 'earthquake machine'? It was in the comics.
This crossover event involves a rematch between Batman and Bane, who is now allied with Ra's al Ghul. It is followed by the one-shot graphic novel Batman: Bane.
In Azrael issues #36-40, a final thread of the Knightfall" plot is resolved in the four-part storyline "Angel and the Bane" and its following issue, Hour of the Quake.
After the events of Batman: Bane, Azrael is tasked by Batman to track down the recently-resurfaced Bane. After meeting, the two men struggle, and Bane gets the upper hand with the aid of a small band of Santa Priscan soldiers and his old henchman Bird. He restrains Azrael and injects him with Venom, with the plan of using him as a super soldier to take over Santa Prisca. Azrael is able to resist addiction to the drug and eventually conquers Bane and flies him back to Gotham City. They arrive just as the massive earthquake occurs. Bane attempts escape but is unable; as a last-ditch effort he unsuccessfully tries to convince Azrael to form a partnership. Instead, Azrael reaffirms his dedication to Bruce Wayne.
The funny thing is, if you go and read the article here,
http://en.wikipedia.org/wiki/Knightfall
Batman supposedly recruited somebody else to take up the mantle. Joseph Gordon-Levitt anyone? This person, Jean-Paul Valley, was basically a rent-a-cop at WayneTech headquarters. Valley, however, had extensive training from a secret society of assassins when he was younger. He was brainwashed though, so his physical conditioning was extreme. The only thing that's not in support of this theory though is the fact that Valley became Azrael, a vigilante anti-hero.
http://en.wikipedia.org/wiki/Azrael_%28comics%29
So basically, could JGL be playing Valley, who takes over as Batman when Bane "breaks the bat"? To end this section, I leave you with another excerpt.
Valley is sought out by Bruce Wayne who grants him money and resources to explore his origins. Along with Brian, he discovers the evil conspiracies within the order of St. Dumas, and they help a nun named Sister Lilhy escape. With the help of Ra's al Ghul he discovers that he is a genetically engineered test tube baby, and his genes have been spliced with those of animals.
To make the connection, here:
Ra's al Ghul is connected to:
-Bane, who needs Venom
-Valley, who was raised by the League, who
-Takes over the Bat Mantle after
-Bane destroys Batman, and then
-Bane gets weaker and weaker because he needs
-Venom, and has adverse side-effects (old, weak, raspy)
Don't know if that makes any sense, but you just don't assign an actor like Joseph Gordon Levitt and have him be an extra. I mean...seriously. All I can say is I think everybody needs to take a chill pill about this. How can you doubt this movie after The Dark Knight broke records and rocked the world? Don't you think Christopher Nolan is smarter than that?