While you worry about survivorship bias, you also want to be careful about confirmation bias :). If you only know miserable PHDs because you know more people who been in to bad programs or so-so schools then world would look very gloomy indeed.
I don't understand your point. Could you explain it, and hopefully in context of my comment at https://news.ycombinator.com/item?id=8722219 which provide some links to research which suggests that "67 percent of graduate students said they had felt hopeless at least once in the last year; 54 percent felt so depressed they had a hard time functioning; and nearly 10 percent said they had considered suicide, a 2004 survey found. By comparison, an estimated 9.5 percent of American adults suffer from depressive disorders in a given year, according to the National Institute of Mental Health."
Some of the research was for UC, which has neither a bad program nor is a so-so school.
Carl Vogel - one of the people questioned on the site - does too, in the comment: "The world is full of miserable grad students. Stressed-out, depressed, uncertain about when or if they’ll graduate and what will happen to them when they do. Far more people go into Ph.D. programs than should."
Vogel is the least optimistic about graduate school of the people interviewed, and also the only one who is neither a PhD nor a current PhD student. This is in line with harveywi's comment about survivorship bias. Your response assumes the same bias, by only considering those finish a PhD from a top school, and diminishing the 50% who did not finish by saying they were "underqualified" or solely at fault for making a suboptimal decision, not recognizing that resolving that question of staying in school (and the potential to be hired at Google) vs. leaving (and being branded 'underqualified' by people like you) is no simple matter.