I was testing this with normalized Blinn-Phong, not a microfaceted BRDF
Blinn-Phong is the microfacet version of Phong. Blinn-Phong describes the percentage of microfacets oriented towards the halfway vector, cause these are the only microfacets reflecting light into the eye. So if you are extending your already partially existing microfacet BRDF by a fresnel term, you should use the microfacets normal, aka your halfway vector.