I think the issue here is not about the relevance of the exam but the fact it appears casa have changed something recently that has resulted in an abnormal fail rate. If this is the case they need to explain what has changed so providers of the training can adapt the training to suit.
Self study is not for everyone. If you fork out the coin and the time to go into full time ground school then you should expect a reasonable chance of passing, as has previously been experienced by AFT students.