I know what ground school is like, and it was without a doubt the most intense six months of my life. Significantly more stressful than school and University. Like Rudestuff says, it's not supposed to be easy. One of my friends in the USA was studying to be a doctor, and he complained to his professor about why he had to study calculus as part of his medical degree. The professor replied "It's to stop morons becoming doctors!". Take it as you like, but ATPLs will inevitably need a lot of blood, sweat and tears. I probably averaged six hours per day of studying for six months. It is, and will be very hard work. I could count the days I had off during that period on one hand. I feel for you guys because from what I hear, ATPLs are much harder than they were a year or so ago.
When I was there the instructors toed the party line and told us to stay away from question banks, as they claimed learning the content through the books was the most effective way to get through the exams. This was very bad advice. In both the school exams and EASAs, the ones who didn't use question banks (or spent very little time using one) ALWAYS had the lowest scores. Question banks are a weapon in your arsenal, so use them IN ADDITION TO proper study.
What I will say is that it would be very, very foolish to rely solely on a question bank for study. Reading, highlighting, making notes, and understanding the principles is 75% of the game. Especially with the new question formats. The other 25% is learning the how to answer, and get around certain types of questions. This extra help is what pushes your score above 75% and gets you the pass. This is what question banks come in handy for. Literally memorising thousands of questions may have got people through in the past, but it's just not enough now. Even prior to the new question formats, I saw students do nothing but hammer the Bristol QB for a week before exams. And fail four or five exams.
Put in the work by using the books and material, then brush-up and test your knowledge through the question banks. It will take A LOT of time and effort, but that's the nature of the ground school beast I'm afraid.