This is straight from the Qantas web site regarding stage 2.
Sample questions are included at the beginning of each section and these should be studied carefully.
The amount and nature of preparation done for selection assessments is at the discretion of individual candidates, however the following information may be of assistance:
The Psychometric Assessment Practice Leaflet contains practice questions, which may assist candidates with preparation for the Psychometric Assessment.
The fact that Qantas has put these sample questions on their web site is to encourage applicants to do thorough preparation on the style of questions they will be tested on. ie to maximise their chances of success. It's all there in-front of everyone. The PATS course just takes some of the hard work out of preparing your own prac questions.
preparation done for selection assessments is at the discretion of individual candidates
PATS fits into this criteria. Why wouldn't you want to do everything in your power to improve your chances. The course is a bit expensive but if it gets you in then it's a drop in the ocean. If you are not actually mentally capable of successfully completing the initial training then the PATS course wouldn't be much help in getting through stage 2 anyway. It just seems to highlight any areas you need to work on or confirm that your prep was on the right track. Its all good either way.