Questions banks were always a must and the recent new questions that came out over the past few years confirmed it. Dubious English, sometimes very unclear questions and even less clear answers available.
Again this is exactly it. I used the question banks a lot, after having a look through my books to get an idea of the topic and build a mental map of the sections and concepts, I then used the banks in order to refine this knowledge to effectively apply it to the EASA questions.
When I and I think many others say to use the question banks, we do not mean to memorise 3000 answers for one sitting - no. What I at least mean is to be familiar with the sort of questions they ask on a particular topic, and you do that with the bank. I was able to score high marks in all tests, not because I had memorised the answers (I forget most, except for the crazier questions that seem to stay in mind), but rather I have learned the material through trial and error with the question banks and seeking to understand why I was wrong if I got a question wrong. Over time you do understand the topic quite well (unless you aren't trying to see why you're wrong). I would say I have a decent understanding of all the topics I just passed, I know full well that when the questions popped up on the screen, I wasn't asking myself "where have I seen this and what was the answer", rather I understood the topics and was able to answer it anyway, and where this was tricky with multiple correct answers, seeing it before and knowing what the examiner wants from you helps sometimes.
To sum it up, question banks help you refine the topics and concepts you really do need to know and that get asked most often. Without such a guide you couldn't possibly narrow down your study to what is the most important.