Sensitivities of the D + H-2 cumulative reaction probability (CRP) are calculated for total angular momentum J = 0 and 6 to test the applicability of the separable rotation approximation The CRPs and their sensitivities are then thermally averaged to obtain sensitivities of the log-normalized rate coefficient using a single J. This approach has great promise of being a simple, yet accurate, method of providing reliable feedback information to quantum chemists without resorting to full-dimensionality quantal calculations. On the basis of our sensitivity analysis, we propose three potential energy surface (PES) modifications which should remove the remaining discrepancies between the experimental and theoretical rate coefficients, especially at the high temperatures, Interestingly, none of these potential modifications lie at a particularly "high"-energy region of the PES as was previously thought.