Current blended teaching evaluation faces persistent challenges, notably the overemphasis on summative results at the expense of process, a disconnect between instructional objectives and assessment, and superficial online interaction. To address these issues, this study adopts the theoretical framework of Outcome-Based Education (OBE) alongside the Community of Inquiry (CoI) model. Guided by the principle of “reverse design,” an integrated evaluation system was constructed, encompassing pre-class, in-class, and post-class formative assessments alongside summative evaluation. Drawing on a sample of 160 students enrolled in the “Introduction to E-commerce” course at LNNU, this research investigates the relationship between evaluation metrics and learning outcomes. A mixed-methods paradigm was applied, utilizing 16 weeks of multi-dimensional behavioral data and final grades. The findings indicate that: (1) both platform access frequency and offline collaboration participation are significantly and positively correlated with academic grades, revealing a high degree of isomorphism between online and offline engagement; (2) video viewing duration positively predicts academic performance, whereas the volume of forum posts exhibits only a weak correlation with grades, suggesting that online interactions largely remain at the social level and fail to translate into cognitive depth; (3) formative assessment correlates significantly with summative assessment, validating the supportive role of continuous process evaluation in achieving learning outcomes. Based on these findings, the study proposes strategies including strengthening OBE-driven reverse design, enhancing online cognitive presence, and deepening formative feedback, thereby offering empirical evidence and a practical paradigm for evaluating blended teaching quality.