In this study, several performance analyses are conducted on all-dielectric absorbers composed of cylindrical-, elliptical-, square-, rectangular-, hexagonal-, and octagonal-shaped dielectric resonators. These performance analyses include the numerical investigation of the change in the resonance frequency and the absorption peak level with respect to the changes in dielectric constant and loss tangent, respectively, in the WR-284 rectangular waveguide setup. In addition, the designed structures are also analyzed in a free-space simulation setup to present the differences that come from using different boundary conditions and excitations. The analyses reveal that the absorption spectra behaviors are similar in response to changes in dielectric constants and loss tangents among the studied geometries. Absorption peak levels of the observed higher-order resonance modes are highly dependent on the resonator geometry. On the other hand, the free-space simulation results reveal that the designed structures have negligible cross-polarization components, hence they do not practically contribute to the absorption spectra. Moreover, absorption, reflection, and transmission spectra are highly affected by differences in the simulation setup and accordingly by the excitation signal for all resonator geometries. In addition, behavior of the absorption spectra for all the dielectric resonator geometries are investigated under the oblique incident wave for TE and TM modes. It has been noticed that the absorption spectra are nearly independent of the angle at lower incident angle values. It is believed that these analyses will contribute to the sensor studies based on all-dielectric absorber designs.