I've got a serious problem with the statement 'ein chavush mattir atzmo mibais ha'asurim" Rashi in the story of Yishmael "ba'asher hu shum" says that the best tefillo is that of a cholleh for himself, even more than other's on his behalf. So if a tefillo for yourself is the best, why would there be a rule of ein chavush?
Excellent question! Your question is addressed by the Rishonim in Vayera. Chizkuni (Bereishis 21:15) answers that the reason our Gemara states that 'ein chavush mattir atzmo mibais ha'asurim' is because most sick people cannot concentrate properly on their prayers. If they do, their own prayers are answered before any others.
Support for this answer can be drawn from Rosh Hashanah 18a: "Two people fell sick, both prayed, why was one saved and the other not? Because one prayed properly and concentrated on his prayer, while the other did not."
Gmar Chasimah Tovah,