This paper deals with hierarchical bases for the preconditioning of the Electric Field Integral Equation on arbitrary 3D meshes with triangular cells. The basis functions are constructed on subsequent groupings of the initial triangular cells, which give rise to a nested family of meshes with non-simplex cells. The previously published hierarchic set of basis functions acts as a preconditioner for dense meshes, but it may lose effectiveness when the domain of the most extended basis functions is comparable with the wavelength, thus limiting the application range of the method. The present work undertakes to overcome this limitation by introducing two tiers of basis functions, related to the hierarchic cell groupings. By suitably modifying the grouping algorithm a coarser level is obtained, on which non-hierarchic basis functions are defined. Hierarchy in the basis function defined on detail meshes is preserved instead. Numerical results show the effectiveness for structures with electrical sizes beyond the resonance region.