Please recognize that I do not refute the fact that God heals or that He has given this authority to His chosen people, however, with that being said, I do not agree with your assertion that God never "inflicts" one as a means of correcting a fault in them.
How do you explain
Exodus 3:24-26, wherein it is explicitly written that the LORD sought to kill Moses for failing to circumcise his youngest son?
While we aren't told the manner through which God sought to slay Moses for his negligence in keeping the commandment of circumcision, can there be any doubt that it must have been through physical ailment of some type?
How do you define chastisement?