Are Nora’s duties to herself really more important than the other roles (wife, mother, and friend) she plays?

Well, it depends. Do you believe that one's duties to oneself or one's duties to others are more important? For Nora, she realizes that she has been a pawn manipulated by the men in her life, and that she's been commanded by them since her youth. In the end, it occurs to her that she was her father's "doll" who then became her husband's doll, she's never really been happy, and she's only been valued because she's been so obedient and compliant. She's been who society, embodied by her father and husband, wanted her to be rather than figuring out who she really is and then being that person. Because she's been denied this opportunity as a result of her femininity, she does seem to deserve the same chance as a man to achieve self-actualization.
However, she does have children to consider, even if we discount her husband. While Nora might seem cold for abandoning her children, we must consider that the world has been cold to her. Her opportunities for living have been circumscribed, and she rebels against the limitations society imposes on her. This seems to me to be very brave, and it is only the existence of her children that problematizes her decision (in my view).