A number of Heusler-type phases, e.g. TiNi2Sn, TiNiSb, ZrNiSn, TiFeSb, NbCoSb, which, for a long time, were considered to be stoichiometric with point composition, are characterized by homogeneity regions and/or off-stoichiometry. Traditional high-throughput DFT calculations aim at the discovery of new fully ordered point composition Heusler-type phases and their potential intrinsic and extrinsic defects. In order to extend the application of DFT methods for determination of structural disorder in half-Heusler and full-Heusler phases we propose a new multi-way approach. It is based on evaluation of the crystal structure model that is used in DFT calculations by getting the best agreement between a set of theoretical and available experimental data (e.g. concentration dependencies of the lattice parameter, homogeneity regions, physical and mechanical properties). This approach allows to determine the model of structural disorder in Heusler-type phases, explain or predict the presence of the homogeneity regions or off-stoichiometry, and reveal the mechanisms of solid-solution formation.