I take it that believers do not ascribe such inconsistent results to capriciousness on God’s part, but rather to their own limited capacities to understand God’s ways: “Thy Will be done.” But why continue directing any psychic energy to a being so lacking in sympathetic correspondence to human needs and values. It will not do to say: “God does respond to our prayers, but in ways that we cannot fathom.” Saving a child from cancer and letting a child die from cancer cannot both be a sympathetic response to prayer; if we had wanted a stricken child to die in order to secure an earlier entry to heaven, we would have said so. And if premature death from cancer is such a boon, why doesn’t a loving God provide it to one and all?
Now believers can answer those questions in a self-consistent way. Before they can address McDonald's first and quite common question, they should begin with acknowledging the obvious.
Almost by definition, miracles involving tangible exceptions to the natural order must be rare. The very term 'miracle' comes from the Latin miraculum, meaning 'a marvel', and we don't marvel when things happen as the natural order would lead us to expect. We marvel only at the favorable exceptions. Second and more substantively, we cannot expect regular exceptions to the natural order, whether favorable or unfavorable. If we could, the natural order would cease to be the natural order; and not even the most fervent religious believers claim that God will destroy the natural order before Kingdom Come. Hence, not even believers really expect God to answer most prayers for miracles in the way the petitioners explicitly ask. Of course, many unbelievers object: "So much the worse for the natural order." That's really a way of posing the so-called "problem of evil" as an objection to classical theism. But such an objection has force only if it be assumed that our utility calculations are better than God's. Believers need not take that assumption seriously.
Nevertheless, defenders of the faith are not done demonstrating their self-consistency. For the most common rebuttal to the argument I've offered so far is to cite biblical passages such as today's Gospel. Jesus not only did healing miracles in response to faith-filled requests; he is generally taken to have assured believers that if our own requests are faith-filled, we can expect marvels from God in response. But not even the most devout petitioners are usually answered with the marvels they're actually seeking. So, if we take Jesus at his word, then the fact that the vast majority of such requests go unfulfilled should be taken as evidence that they weren't filled enough with faith. Or so the argument goes—and it isn't an argument offered only by skeptics. In some Christian quarters, mostly evangelical and pentecostal, people really believe that if they just believed hard enough, they'd get what they're asking for. So if they don't get it, they conclude that they didn't believe hard enough. That may well be true in this or that case; but if my argument in the previous paragraph is correct, it could not be true in the generality of cases. To believe it's true in the generality of cases is, I think, silly and destructive. For the most part, we cannot "believe" God into doing such things for us. That would be magic, and Christians are not supposed to be magicians. It could hardly be otherwise. How, then, is a believer to show that her faith is at least consistent with what Jesus is recorded as having said and done?
Not a few Christians, mostly mainline or conservative Protestants, believe that "the age of miracles" pretty much ended with the death of the last of the Apostles. For the purpose of such miracles was to signify the occurrence and meaning of the central event of divine self-disclosure: what theologians often call "the Christ-event." Now that divine revelation is definitive and complete, there is no need for a proliferation of healing miracles. The "ordinary means" of faith and personal conversion are enough for appreciating what Jesus' miracles signified: the tangible presence of the God-Man and the meaning of his main message, which is God's merciful and healing love for us. Once that message was got across by the Christ-event as recorded in the New Testament, the natural order could and should be left undisturbed.
There is some element of truth in that view—which I shall call the "cessationist" view (CV)—but I don't think it will ultimately do. For one thing, it is not the traditional Christian answer. For 1,500 years before the Protestant Reformation, Christians took for granted that healing and other miracles occurred surprisingly often in response to prayer—usually, petitions for the intercession of the saints with God. Devout Catholics and Orthodox still take that for granted. Indeed, by no means all Protestants today accept CV: the fastest-growing segments of Protestantism are just those whose adherents seek and expect miracles. It's easy to chalk that up to wishful thinking; but the fact is that CV has never been the prevailing view among Christians. The relative dearth of miracles today can be explained by the same reasons which explain the relative dearth of miracles generally. Of course CV is not entirely without merit. If Christianity is true, then we would expect more miracles from Jesus and the Apostles then in latter times. But it doesn't follow that we can expect none; nor do Christians in general believe there are none.
The only way, I believe, to preserve the traditional view's self-consistency is to show why the relative and necessary rarity of healing miracles since the time of Christ should not be taken as evidence against what Jesus promised to those with "faith." And one can do that only by pointing out that, assuming that Jesus' promise applies to his latter-day followers, he cannot usually answer prayers made today, in the spirit of the centurion or the woman with the hemorrhage, in the way that the petitioners want—at least not with anything like the frequency with which he found it expedient to do them with while still on earth. To do so would be to destroy the natural order that he himself wills to continue, and thus to "immanentize the Eschaton" before he's ready. So, if he does answer them favorably, that must be in some way other than what the petitioners are explicitly seeking.
This is where McDonald's first question becomes not just directly pertinent, but also applicable to petitionary prayer generally. She asks: "[W]hy continue directing any psychic energy to a being so lacking in sympathetic correspondence to human needs and values[?]" The answer is that God is not lacking in "sympathetic correspondence" to our needs, but wills to re-orient our values to align more closely with our needs—the chief of which is redemption, which requires faith. After the Christ-event and before the Eschaton, redemption does not usually consist in miraculous physical healing and, for reasons I've already given, could not. But that doesn't mean it doesn't happen on occasion. It happens just often enough to constitute a ratio credendi for those already moved by grace to grasp the main point of such miracles. That point is, as Jesus said in response to a question raised about his restoring sight to the man blind from birth (John 9: 1-41): "to show forth God's mercy." But that is shown forth in other ways too: chiefly by the lives of those who have truly accepted divine mercy by means of repentance and faith.
Needless to say, that invites another objection implicit in McDonald's last question: if what God does, or fails to do, for one person is what's good for that person, why not for that other person too, who might well "need" it as much if not more? I shall call that the "arbitrariness" objection, or 'AO' for short.
The Christian answer to AO can only be that God's perspective is more unlike than like the one we naturally adopt. We cannot always or even often know how each of us as individuals will serve best as signs and instruments of God's redemption of the world. If we did, we would enjoy a perspective that we could not fully share even in heaven—even though the blessed in heaven presumably share more of it than anybody still in via. Accordingly, AO is a sign of lack of faith. But notice that miracles were never promised to those who lack faith. So, AO is not only misguided but self-defeating. By implicitly tasking God or believers with explaining God's methods, it precludes the very state of mind necessary for getting an answer that might otherwise be satisfactory. That is the lesson of Job.
Of course that leaves open a final, perennially vexing question: how do petitionary prayers influence God? According to classical theism, God's actions are eternal and unalterable, so that we cannot literally "change his mind." To that question, the only reasonable answer is this: God eternally and unalterably chooses, by lights infinitely greater than ours, how he will favorably answer prayer that he eternally and unalterably knows is offered in genuine faith. And in most cases since his appearance on earth, that will mean that people are "healed" in ways knowable only to the eyes of faith.