  The closed-form $T$ matrices in the $^3S_1$$-$$^3D_1$ channels of
EFT($\not/!/!/pi$) for $NN$ scattering with the potentials truncated at order
$\mathcal{O}(Q^4)$ are presented with the nonperturbative divergences
parametrized in a general manner. The stringent constraints imposed by the
closed form of the $T$ matrices are exploited in the underlying theory
perspective and turned into virtues in the implementation of subtractions and
the manifestation of power counting rules in nonperturbative regimes, leading
us to the concept of EFT scenario. A number of scenarios of the EFT description
of $NN$ scattering are compared with PSA data in terms of effective range
expansion and $^3S_1$ phase shifts, showing that it is favorable to proceed in
a scenario with conventional EFT couplings and sophisticated renormalization in
order to have large $NN$ scattering lengths. The informative utilities of fine
tuning are demonstrated in several examples and naturally interpreted in the
underlying theory perspective. In addition, some of the approaches adopted in
the recent literature are also addressed in the light of EFT scenario.
