The miscibility of two macroscopic phase separated polymers, a propylene-ethylene-diene terpolymer and an atactic polypropylene, has been investigated by a combination of several solid-state NMR techniques. Carbon-detected proton T-1 rho and carbon-detected proton T-1 in systems conditioned by two-dimensional heteronuclear wide-line separation (WISE) were used. Both techniques are sensitive to spin diffusion between phases, with WISE being suited to making it stand apart from the basic relaxation process. These two techniques yield similar but different assessments of the presence and amount of phase separation present. This is not surprising considering that they involve different relaxation time scales, from milliseconds to seconds. An additional comparison is made with differential scanning calorimetry and xenon NMR results, which also address this problem. In addition, the WISE data permit an estimate of the aPP domain size.