I think the problem is the definition, not the position of God. Quotes like, "If I ascend up into heaven, thou art there: if I make my bed in hell, behold, thou art there." (Psalm 139:8) refute the very idea that God is not present in Hell, and even if that were not the case, saying that "Hell is separation from God," is a contradiction to the very notion of omnipresence (and it is very hard to say that omniscience and omnipotence can allow for a denial of omnipresence).
Similarly, saying that Hell is a place without grace or mercy is mistaken. For *at no point* in scripture does God ever say that man loses his intrinsic worth (if he did, he could not be redeemed, nor would there be value in his redemption) or that we are no longer the likeness and image of God. If we are honest and admit that our very existence is a gift from God, then we must view Hell as a necessary continuation of the divine Grace, despite our failings (which is why God does not simply make it as if we never existed).
Rather, Hell is a place of suffering, torture, and despair. It is a state which results from the rejection of God (though it is *not* the rejection itself, otherwise we find ourselves in the same problem described above). It is called, an ever-burning fire, and a place where the soul is perpetually consumed. As Christ was fully human, he would have been able to experience these in their perfection and, most importantly, he can experience these without self-contradiction.