The first problem is that too many villains are too sci-fi'ish. This would include villains like Clayface, Mr. Freeze, Killer, Kroc, Man-Bat, and Poison Ivy. These characters simply cannot exist in Nolan's hyper-realistic world, nor would the Public want them to exist because the public prefers hyper-realism over the sci-fi/cartoony style
Second, too many characters are just not well known enough. Much of the Public didn't even know about Scarecrow, so do we really think that the Public will know about Anarky, Hush, and Black Mask? Probably not.
Third, too many characters are simply not menacing enough. Characters like the Riddler & Penguin are the main examples. Which is more menacing, Riddler's riddles, or Scarecrow's nightmares? Penguin's birds, or Anarky's anarchy and lawlessness? Appearance wise, Penguin is comical/funny looking. Granted the Joker jokes, nothing about the Joker's appearance is comical orfunny. Nolan's joker was menacing because he was more of homicidal maniac (with a menacing appearance) rather than as the court jester type. Nolan's Joker was really a nihilist that looked like a jester. But the Joker is not an option given Ledger’s death and Nolan’s recent statements. So how does Anarky fit it? Well, we all know that nihilism will lead to anarchy
Enter Anarky. Again, he's not well known. But that's the price we pay to retain hyper-realism and the menace factor. In the comics he's a teenager, but that doesn't have to be the case in the movie. But most importantly, Anarky’s modus operandi fits in with the ending of “Dark Knight.” “Dark Knight” ended with the police chasing Batman. For philosophical reasons (like V in "V for Vendetta"), Anarky believes the government should be destroyed (whereby anarchy will ensue) because he believes all government is corrupt all the time (unlike Raz al Gul, who believed that only some cities were corrupt at their financial peaks).
Imagine the action scenes and plot! The government is hunting Batman down in pursuit, and Anarky intervenes their hunt by killing them and saving Batman! This causes Batman to hunt Anarky, the government to hunt Batman, and Anarky to hunt the government by blowing up cars and FBI buildings! It's a three-way circle! For Anarky, the enemy of the Government (Batman) is his friend. But for Batman, the enemy of the Government (Anarky) is not his friend.
Anarky's appearance is dreadful as well. His mask is similar to V's (V for Vendetta) Guy Fawkes mask, and shares V's anti-Government views. But he has this red Catholic Pope robe and hat on, which adds to the eeriness. Intellectually, he would be the smartest of all villains – smarter than Edward Nigma. He doesn't quote jokes and simple riddles, but political philosophers such as Aristotle and Karl Marx. He's justifies (or tries to at-least) to provide a philosophical foundation for his anarchism. He’s deep, yet misguided. He’s our next Batman villain.