Following Dynamic Systems Theory (Thelen & Smith, 1994) and Sociocultural Theory (Vygotsky, 1978), this study compared the developmental paths of low and high-achieving EFL individuals and dyads, considering production features of complexity, accuracy, and fluency (CAF). The participants included six MA students majoring in Industrial Design at Iran University of Science and Technology. They were assigned to individual and pair groups; one learner with minimum performance on CAF features (Low-achieving Individual; LAI) and one learner with maximum performance on CAF features (High-achieving Individual; HAI) were assigned assignments to compose 10 tasks over the semester individually. Furthermore, two learners with minimum performance on CAF features (Low-achieving Pair; LAP) and two learners with maximum performance on CAF features (High-achieving Pair; HAP) were asked to write on 10 tasks over the semester in pairs. Their developmental paths in terms of CAF features were tracked. The findings demonstrated unique developmental paths with oscillations and trade-offs between the components of writing proficiency, and the possible influence of collaborative performance and participants’ proficiency level in the differences in the developmental paths. They showed that LAI and HAI outperformed in fluency and complexity over time, and HAP outperformed in accuracy. The study concluded with implications for pedagogy, suggesting the uniqueness of the developmental paths of each learner and the need for evaluating writings in terms of a multidimensional lens.