This is depressing to read. If there's an error in anything, I make sure that stuff is up-to-date, and generally post a news item telling them of an error, where it is, and the new version of the document.
As an instructor, it's generally pretty easy to tell if an exam is too hard or easy, at least for me. I look and see if the average was like in the 70s. That's generally a good exam. If the average is in the 80s, it might be too easy. If the average is in the 60s... I consider cutting a problem. At least in the exams I've written that hasn't happened. At my university exams go through a lot of drafts. I think that is because we have a lot of instructors for the same course, so there's more exam drafting.
Other classes, though, there might just be the Physics 201 teacher, and that's the person. They write the exam, and there's no one to really look it over. And Young Bard, I totally agree, that teacher sounds awful.
I think a good solution is to make sure, as a professor, that your expectations are reasonably clear. If you set out clear expectations on what difficulty of problems you expect students to do, they will rise up to the occasion, and generally be really thankful you were clear rather than mysterious. Your examples of teachers do sound particularly bad. Though, as I'm sure you know, there are definitely students who don't do the work and then always complain about there not being enough help. (This is a consistent thing on evaluations, despite at my University there being more resources than ever before.)