ACTL/FINS @ UNSW 3rd year in 09. class of '06.
I'm gonna say something different regarding Ext II and ACTL. Ext II has a rather non-actuarial related syllabus (conics, mechanics, volumes etc) and is significantly easier (considering the time span to content ratio and raw difficulty). As a sole indicator, it is rather unreliable, considering Ext II is just doing past papers (although uni sorta tends to be like this).
What should be considered, will be how dedicated to study you will be over the next 3-4 years (although the 'hecticness' begins in 3rd year). There has to be a motivation other than cash, such as a genuine interest in the science or even interest in the challenge itself (I chose the latter). This may sound cocky, but I've attended 5 ACTL lectures in the past 2 years, and have got all my exemptions so far (barring CT7 Economics). However, it is the study at home that is most important. Followed by how lucky you are with your tutor. Not to mention any names. Bill W, B Wise. 17/100 class average.
As for mark distributions, they are just like the HSC (based purely on rank). I've forgotten where I heard/read this, but from what I know, they basically set aside a number of exemptions given, mere passes, and fails. They then rank the students based on their raw exam marks. Draw cutoff lines and the appropriate ranks, and distribute the grades from there. (Note: Can someone confirm this?) From past experience, they give half the students exemptions. So you essentially just have to get over the mean mark to attain it. Btw, this is not as easy as it seems. In the HSC, you may have been the big fish; but in the ACTL pool, basically everyone is a 95+, with the same desire to get exemptions.
Feel free to argue. I've written this much, surely I'll get flame back.