As someone who has 8 atpls done and 6 more to go (so roughly right in the middle of it), I agree that there are some very bad exams and very bad questions, but not all of them are the like. I was sitting AGK for example, couple of weeks ago - lots of new questions, I'd say a good 1/3rd not in your QB, but they were good, decent questions, nothing bar one question, really phased or shocked me - if you read your book and do your revision courses, you will do fine! At least this works for the vast majority of people
The goal is to understand the subject - what's the point in memorizing the QB? There's no QB for your job interview, so you might as well get the most out of your ATPLs simply to be prepared..
that being said, QBs are really valuable and I will admit, that even thou I understand the subjects, I wouldn't have first time passes in all subjects so far with out them..