That's the great thing you can count on when it comes to Nolan; he will always throw in some sort of physical representation of his symbolism.
With this example, while we do see Batman's actual fall from grace from being Gotham's protector, we can now see him as what most of Gotham probably sees him: even more mysterious than before.
It must be a hard thing to grasp being a citizen there that the dark protector you have come to love and count on keeping the city clean, has let it become a playground for Joker's brand of order (or lack thereof). From one extreme to the next, it is then shown (we assume) that Batman has killed an experienced cop (Wertz), 2 mobsters (Maroni and his driver) and now Gotham's beloved new DA who single-handedly put away over 800 criminals at once.
Top this upon all the deaths and destruction occurred since the beginning of Joker's threats; Commissioner Loeb, several cops, Judge Sirillo, and others as well as destruction of the city's main hospital. Batman has fallen from the highest of highs to Gotham with Dent's death being the final straw.
At the same time however, we see reflection of the opposite direction with those around him who know his secret and/or trust him.
Alfred burns Rachel's letter to keep Bruce's faith from shattering. Fox smiles as his trust is rewarded with the sonar servers being destroyed. This is even represented when Gordon is breaking the Bat-Signal. His first hit, which could have destroyed it, fails to do so; showing his reluctance to defame the character of the hero he has come to respect throughout his career since Lieutenant
To answer the question, is this a representation of Batman's fall? Yes.
However, with the title of the newest film being Rises we will soon witness his return to this former grace as he attempts to save the city from the destruction Bane is sure to bring.
