Re: Does Bane being a PURELY physical threat hamper him as a villain?
To the OP: Not at all. Ra's Al Ghul and Joker had reached their apotheosis, so to speak. They had their goals--Ra's rubbing out the corruption in Gotham through any means necessary, Joker demonstrating how anyone could be made degenerate by one bad day. Bane, on the other hand, didn't arrive in Gotham with such broadly reaching messages.
Bane's was more personal: He and Bruce were both rescued from prison by Ra's. Ra's trained both in the League. Ra's distaste for Bane--a monster that emerged from the hellhole where his wife was raped/killed--led him to excommunicate Bane. In contrast to Bane, Ra's wanted Bruce to be at his side when he attacked Gotham. Bruce rejected the opportunity and place in the League Ra's offered him.
Bane was never even given that. Yet, despite the honor offered by Ra's, Bruce rejected the offer. This is where Bane's motive comes in. In leading his mercenaries to Gotham, Bane sought to prove himself the superior man to Bruce. This happened in the sewer fight where he basically took Bruce apart at his leisure. Furthermore, Bane was the first to become the symbol that Bruce wished to be: Bane inspired the people to rise up against corruption.
Through completing Ra's Al Ghul's mission, Bane sought to prove himself the superior man to Ra's. Ra's tried using the economy to bring Gotham to its knees. He tried using the Fear Gas to cause the citizens to tear their city apart. He failed on both counts, thanks to Batman. Bane was also thwarted by Batman in the end; however he enjoyed a greater measure of success than Ra's. He took in the orphans who were kicked out of the orphanage and the lower class. He galvanized the people to strike back against the rich. Under Bane, the Gothamites were in full possession of their mental faculties when they turned on each other.
My interpretation is based chiefly on the dialogue between Blake and the orphan in the beginning about work in the sewers, Bane's dialogue during the sewer fight, the backstory as given by Talia and Talia's line to Bruce: "Innocent (innocence?) is a strong word to throw around Gotham, Bruce."
Edit: Shaun, your feelings on following TDK with Riddler echo my sentiments in the couple of years after TDK's release when much of the speculation revolved around the Riddler being the villain. I just wasn't excited for those films. However, I think in the reboot series, Riddler should be Batman's stepping stone from mob/gangsters to freaks and flamboyant mobsters.
Don't let the death of the three horses be in vain-see The Hobbit: An Unexpected Journey.