We study the dynamical properties of pointlike defects, represented by monoatomic chalcogen vacancies, in WS2-graphene and MoS2-graphene heterobilayers. Employing a multidisciplinary approach based on the combination of ab initio, model Hamiltonian and density matrix techniques, we propose a minimal interacting model that allows for the calculation of electronic transition times associated to population and depopulation of the vacancy by an additional electron. We obtain the "coarse-grained" semiclassical dynamics by means of a quantum master equation approach and discuss the potential role of virtual charge fluctuations in the internal dynamics of impurity quasidegenerate states. The interplay between the symmetry of the lattice and the spin degree of freedom through the spin-orbit interaction and its impact on charge quenching is studied in detail.