To answer the question of whether Sula is a heroine, I have to reply both yes and no. She is a savior figure, but only insomuch as she unifies through hatred. When she returns home to the Bottom years later, her disreputable actions invoke the ire of the townspeople, and they rally as one against her. However, her heroism (or anti-heroism) fails upon her death, when the common dislike of Sula is suddenly dissolved, along with the unity amongst the people that was formerly enjoyed.
The only lasting contribution of Sula's heroism is her dying conversation with Nel. She tells Nel that women everywhere are dying like stumps, because of their refusal to acknowledge their ability to remain independent. Sula charges Nel with this offense also, and states that Jude, Nel's ex-husband, was a space filler, nothing more. This kind of discourse raises many questions about the nature of good and evil, hiding them in ambivalence rather than shedding new light. Sula claims she is good, that has always followed her own will and desires rather than bend to social constructs. In her mind, she is only partially responsible for the dissolution of both her friendship with Nel and the marriage of Nel and Jude. In both those actions, another party had a part to play. In this manner, Sula sees herself as a heroine, seeing the submission to society as an act of anti-feminism, thereby marking society as phallocentric and in opposition to women, especially, in the case of Sula, black women.