There are several different possiblities for both of these characters. John, husband and doctor to the narrator, could represent a rather stifling and oppressive influence on the narrator herself. In that time period, not a lot was known about different mental disorders, and women who had a "nervous disposition" were often isolated, treated as invalids, and not allowed to do the things that they loved. John, a doctor, has this attitude also, and even though the narrator tries to be a "good wife" and obey his dictates, she gets worse and worse. He calls her silly, treats her like a child, tut-tuts her own opinion on things, and asserts his will over her. Granted, it's all done in a nice way, but he is definitely not doing what's best for her. So, possible things that he represents: domineering husbands, ignorant doctors, men with a superiority complex, the anti-feminist, marriage's restrictive nature for women during that time period, and, overall, a bad influence for women who are struggling.
The narrator herself represents any woman at that time period who was struggling with depression or anxiety, or post-partum depression (which they knew nothing about at that time). She struggles with her anxiety and stress, and tries to pull herself out of it, but circumstances and the time period work against her. Doctors didn't know how to properly treat depression, so she becamse the unwitting victim of their misplaced ignorance. Women weren't allowed to be unhappy in their circustances, so she was victim to other people's expectations. Women were looked down upon for writing, so her creativity suffered. So, everything about her time period really conspired against her to make things work; she symbolizes any woman at that time who struggled with mental disorders.
I hope that those thoughts helped a bit; good luck!