This paper presents a novel physically consistent analytical model for two-dimensional (2D) waveguide-fed metasurface antennas that is based on the discrete dipole approximation. The proposed framework extends previous works deriving power-consistent constraints on the magnetic polarizability tensor, leading to closed-form expressions for the effective polarizabilities. The model is validated through full-wave simulations for multi-feed settings, and is extended to a near-field compatible~formulation enabling accurate predictions in the radiating near-field.