Hello
I am not writing this message, as a professor but as a observer. Further many things change from student to student, i am writing this message taking into consideration , average student in audit and experience of more than 10 years in teaching.
Across the year i am flooded with students asking me simple question why I didn’t clear audit or why I scored less in audit?

1. Self Study

There is no substitute to self study, you are sole performer in exams, there is no support of anyone when you write paper. So you need to understand, you need to remember you need to write. you need master subject. Quantum can change depending on grasping power, memory power and ability to concentrate for long number of hours.

2. Volume
Audit is voluminous subject 22 chapters, out of which one chapter includes 45 standards , Module & Notes are generally between 800-1000 pages + around 591 questions in PM (Old Course , As all chapters of new course module & pm are not released)

3.Tricky
It includes variety it includes different types of entities right from General Insurance / Stock Exchange / Mutual Fund / Co-Operative / Bank Audit etc . Different types of Assignments Tax Audit / PSU Audits etc
SAs offer altogether different world of auditing.
Now Articleship offers limited exposure in 1 or 2 areas, and way we do auditing is different from SAs. This makes subject challenging to understand.

4.Results
As per estimates if 100 people fail in group 1 ,60-70% because of audit. I have seen group leaders doing audit of listed companies scoring 28 and giving multiple exams to clear audit subject.

5.Different from Practical & Law
Theory subjects like Audit (800-1000 pg) & ISCA (300 – 400 pg) are challenging because it is 50% understanding and 50% retention. In practical it is 80% understanding 20% retention. Further practical and law are good as we can compare and differentiate different methods and sections. In audit & isca there are plenty of factors for each step of point, and points look similar to other topics. So it becomes big challenge to differentiate / retain and reproduce. IPCC Grp2 results were low, one of the reason was 2 deadly subjects of audit and ITSM in one group and also Articleship pressure.
Only overall / raw understanding of topic is not going to fetch marks, understanding each factor and retaining it and reproducing it is important thing.

6.Student perception & approach
They allocate one week to 20 days for the subject and some may allocate 40 days also. So that goes to 800/40 = 20 pages. Reading / Understanding / Research Behind Topic / Hunting Examples / Thinking about retention techniques and doing writing practice. That too few hours in hand many times because of Articleship

7.Is doing classes a bad thing?
I was a rankholder I went for all subject classes and I guess same is the case with many other rankholders and CAs. In this world, where we have less time we need apt guidance to make ourselves efficient & effective. We go to gym, we go for trainer so that in less time we get our body healthy. Further how much it costs to for class 5000-8000, if there is financial problem, people may help you out. What you gain is knowledge , techniques which saves your time, gives more time for overall studies and increases your probability of clearing exams drastically.

Solution
Go for proper class / lecture 120 – 150 hours. Do regular self study for 80- 100 hours. Use all examples . charts , techniques provided . do revision / writing practice you are prepared for exams. Never ever do preparations in haste, it will cost you few attempts,  because once you prepare it defines your understanding , depth attitude and approach towards subject. Then its very difficult to change it unless you give loads of time.
Lectures + Notes + PM + RTP should be the Study Plan

Conclusion
You need to assess yourself, scores of ipcc audit cannot be base, I meet n number of students who scored exemption in ipcc audit and now struggling to clear ca final audit for 3-4 exams. You can assesses whether you can clear it with self study.
Read SA 300 series / 400 Series / EDP / General Insurance and write down then attempt questions from PM it will be good taste.
Our books are designed in such a way that they are effective along with live lectures or videos, because we follow notes extensively as we teach.

Please be open to share your thoughts, will take it in consideration