Andrea Dworkin should be credited as an influential activist. She wasn't particularly standing on the shoulders of others with her thoughts on pornography and it's relation to the treatment of women. She brought new ideas to the forefront and fought for women who were being subjected through pornography, which hadn't been done in the past.
Dworkin's claim in her writing is that all sex is a form of power games (i.e. rape) and that men secretly harbor a Freudian fear of the female as a neutered male and subsequently sought to punish them. This theory is not overtly preached, but one cannot but be struck that on many college campuses, an accusation of rape is almost the same as a conviction.
Yes, Andrea Dworkin was an extremely influential activity, because she was so influential that she made a prison close. It was her testimony about an internal examination that caused bleeding, that led for the prison involved to have to close. Her opinions are remembered, and she has done a lot for the rights of women.
I believe Andrea Dworkin was an influential activist, especially for those who agreed with her viewpoints. For me, I can't side with her on her beliefs regarding pornography and I believe those beliefs sully her whole reputation, but there are many who support her and others who ended up adopting her views.
If you equate "influential" with "people noticing you" then Andrea Dworkin is your girl, because she certainly got noticed. As for a feminist activist, she was the type that made people roll their eyes at the movement. There's certainly nothing wrong with the concept of feminism overall, but there are ways of going about promoting it that make you look like an idiot.