For me, at least, I cannot treat the matter so simply. Certainly God establishes rules for the "derech hatevah," the natural way of the world. But, at the same time, as a religious man, I also accept as a basic proposition that God has a hand in all things. "Who shall live, and who shall die" is not for me merely pretty poetry recited from habit. If I accept (as I do) that God determines the fate of humanity both in general and in specific, than Sharon's perfectly natural and explainable stroke is also somehow a product of God's general supervision and management of the world. It is not unnatural for a man of Sharon's age to have stroke, but it is not required either. Why should it happen at this moment, in this time, in this place, rather than a year ago (when it would almost certainly have prevented the Gaza disengagement) or a year from now (after the Israeli elections)?
But to accept that God, in his infinite wisdom and complexity, has set events in motion, does not require me to accept the primitive view of Pat Robetson. If I read in the Bible that because On refused to father children in the name of his brother, God killed him, I can accept that cause and effect. If Elijah calls on God to send fire from Heaven to consume his sacrifice, and fire falls out of Heaven a moment later, I'm willing to call that cause and effect.
But absent such an explanation or even such an obvious and miraculous connection, I find it presumption bordering on hubris to assume that we can so clearly and with certainty fathom God's will. This is made even more difficult if we use a very simplistic and primitive idea of reward and punishment. The incapacity or death of Sharon will have far reaching consequences. Is Sharon merely suffering so that these consequences can occur? Or does God not care about these consequences if all he intends to do is punish Sharon?
All of us who believe in a compasionate, omnipotent, omniscient God have at one time or another struggled to answer these questions. It is the essence of both Eccl and Job? What kind of God slaugthers Job's children simply to prove a point to Satan? And who can prove there really is a God? "Who can say that the spirit of man ascends [to heaven at death] and the spirit of the beast descends into the earth?"
For myself, I have been forced to content myself with the fact that, as a human being, I am simply never going to understand it all. My failure to understand does not make God any less real or more real than my failure to understand how gravity actually works changes the fact that objects dropped from a height on planet Earth fall at a theoretical rate of approximately 32 ft/sec (squared). And while the presence of natural explanations for observed phenomena, such as Sharon's stroke, may make the existence of God "unnecessary," it does not change the fact of His Existence or what I will believe.