How about training TSA personnel before we throw our hands up in the air and declare the situation hopeless?
Yeah, "your average TSA screener seems to be a working stiff, blindly following some not-too-complex screening algorithm in a three-ring binder ..." cuz that's what we told him to do. Hell, the restaurant/bar where I work nights has bouncers who do a better job of screening out undesirables, the underaged and the overintoxicated than the current screeners do. And they aren't well-educated guys who have to "pass a series of exams and ... a several-month course" before they man the door. They may, however, get cited by the liquor board and be held personally responsible for paying the fine for letting the wrong person in the door.
Yeah, there's a problem of scale, but singling out young men--of any ethnicity--and one-way travelers and people who have visited Yemen for educational purposes for further scrutiny makes more sense than randomly selecting every 12th, 100th or 221st person in the line for a full body scan.