Theoretical interpellations: confusions around "gender"

Reading Freitas & Pinheiro (2013) I am questioned by the notions of gender across feminist authorship.
The ways gender seems to stuck people on individual (interaction) relations bypassing the social structures of the gender and patriarchal order seems to concord with the argument of Virginia Ferreira about the useless of the concept of gender.
This slippery concept together with a strict foucaultian perspective on power renders gender as incapable of accounting for the power relations in private sphere between men and women and some analysis slide to wrangles between individuals.
Although affirming a feminist perspective, there is a difficulty to perceive women as a group with less power than men.
On the contrary, Sue Clegg (2006) is particularly clear about the structural relations founded in gender inequalities and the patriarchal order.
I re-read Clegg to gain insights for a comparative paper I am wrestling with and I found it very useful to dialogue with Freitas & Pinheiro. These latter authors present a set of "narratives of violence" extracted from the processual pieces of the charges on gender and domestic violence in Jaraguá, Goiás, within the frame of "Lei Maria da Penha", and analyses them through the concepts of gender and performance (Butler 1990), using critical discourse analysis on juridical texts.

References:
Freitas, Lúcia & Pinheiro, Veralúcia (2013) Violência de Gênero, Linguagem e Direito. Análise de Discurso Crítica em Processos na Lei Maria da Penha, Jundiaí-SP: Paco Editorial.

Clegg, Sue (2006) “The problem of agency in feminism: a critical realist approach”, Gender and Education, 18:3, 309-324, DOI: 10.1080/09540250600667892.