What should be said here is that Heidegger's renunciation of metaphysics did not, in the end, allow him to produce a coherent ontology of his own. His efforts to describe the relation of being to beings in purely immanent terms ultimately added up to very little; certainly they did not provide any convincing answers to such perennial questions as why there are beings at all. At most, all he could do was point to temporality, the ceaseless flow of beings out of nothingness and into nothingness again, and then--in a gesture that often seems as much one of hopelessness as of "piety"--point away toward the mysterious Ereignis, the "appropriating event," that somehow brings this about.
Because he had left himself no room for any kind of language of analogy, which might have allowed him to say how transcendent being shows itself in immanent existence while still preserving its transcendence, and because, moreover, he had decided in advance that one cannot speak of being in other than temporal terms, he really could not escape lapsing into a certain fatalism regarding the history he described. Even he had to admit that, if there is no metaphysically "correct" way for being to show itself, perhaps the age of technology really is the next "proper" moment in being's dispensation. If so, all he could do was hope that there might still be a truly human way of inhabiting the world that is coming to pass.
I looked at Hart on Amazon in order to understand why his comments re: MH are so off the wall. Hart is simply in over his head, and his Christian apologetics are incapable of framing a significant crtique of MH. Move along. Nothing to see here.