I will start by saying I loved the film, think it is interstellar years ahead of today's formulaic comic movies. One of the minor criticisms back then about the movie was the portrayal of female characters. Dark Knight is a macho film. In 2008, it was easy to sweep this problem under the rug. In 2018, it would be difficult in the era of time's up, me too, empowering female characters, equal gender pay and strong female leads.
I don't think critics and others would have forgiven the movie on the wasted potential that was Rachel after her excellent portrayal in Batman Begins as her character was one of the most pointless and non effective female characters in any movie. I had some nitpicks with her
She was just a love interest
Maggie Gyllenhaal was unimpressive in the role, Katie Holmes was much better and I have to say it but yes, far prettier
Unconvincing love story between Her and Dent
Non-effective to the entire plot. I wish Nolan wrote a better reason for Dent becoming Two Face.
I can erase Rachel from the movie and still have the movie 90% as it is. She is that disposable in the film. Progressive Feminists may have raged against this movie in 2008 with all the attention the film received and could have done it major harm.