I would agree that these movies are probably too intense for younger children; but the Batman movie you are referencing was the last one (Heath's Ledger's Joker), not the current one. The source material in the comic books is often far worse...the Human Torch used to roast Nazis and 'Japs' alive on a routine basis back in the early 40's for Marvel (Timely) Comics. Violence associated with comic characters is nothing new...parents just need to pay attention, and many just don't bother. There are FAR TOO MANY children raising children.
Leni