I think that the word hero, as it pertains to this story is a pretty shady term. I think one of the main themes of Sula is that no one is perfect, and that we all have serious issues. If there were any people in the book that were portrayed as wholly good and righteous, without some shadiness or negative activities, there weren't many. Then again, maybe one of the themes of the book is that no matter how good of a person you are, you will always be criticized. In other words, there will always be people who second-guess you and criticize who you are and the decisions you made. This is done by and to most characters in Sula. However, most of the characters in Sula did things that deserved criticizing. This is shown through the townspeople, whose views of Sula turn very negative by the end of the story. For example, they view Sula as a "witch" and her death as "the best news they had heard since the promise of work at the tunnel." I think it is hard to label a woman with this level of a semi-earned reputation a hero.
Another complication of the word hero, are the values that the person has that makes him/her a hero. Different people have different sets of beliefs and values, so different people will view different characters as a hero or not. From my perspective, I would not consider Sula a heroine to be admired or imitated. I think this is an important quality of a hero: that we see value in a part of them that is imitatable. I don't find many of her values and actions worth modeling myself after. However, if one were to read Sula from a feminist perspective, there are some admirable qualities that can be drawn from Sula. For example, Sula leaving bottom to attend college and not coming back for 10 years would break the traditional role of a woman in 1927. This would break the essentialist view of the time that a woman's skills and abilities would be best suited for her to be a housewife. Unless she was going to be a teacher or nurse, they would probably see it as pointless for Sula to go to college. Sula went against traditional gender roles and essentialists who would try to say that it is natural for a woman to seek her niche in the home under her husband. Instead, Sula went off to college, and presumably spent an extra six years away from Bottom. Then, on her reentry to bottom, she appears strong and flashy, looking like a movie star. The people of Bottom didn't like this, and associated it with the plague of Robins. But feminists might interpret this as a negative view due to Sula putting off an ora of power, which again, breaks traditional female roles.