But, the electron cloud is spread out over a wide area, so the bulk of the electron cloud's charge is not necessarily closer to a given electron than the nucleus.
Plus, the fact that DEL(H) > 0 can be verified experimentally. For example, consider the photoelectric effect. When you shine light on a metal surface, the atoms in the metal will absorb photons which will eject electrons from the metal. Since ejecting the electrons (i.e. ionizing the metal), requires an input of energy (a photon), DEL(H) for ionization must be positive.