again you're basing that off of students that are from this forum that would have found it easy. The judges who decide the cut off would be considering the whole state not just a handful of students, and also new syllabus cut offs are usually lower as seen from last years new syllabus papers which all had low cut offs even though some of them weren't difficult.
If you are referring 7/15 for q14 (given the rest was estimated from last year's judges decision), I find it hard to imagine a cutoff below 2-3/8 as the first part was a relatively standard binomial style question and quite similar questions have occurred before. Maybe you are right that the 5-6/7 is too high for the last question due to the last part - I agree that 4-5/7 might be more suitable giving a 55 cutoff.
Edit: this estimation is based the difficulty compared to last year's judges decision. Additionally I think this forum while not representative of the average student for sure, does give a sense of the band 5-6 student, which would be quite a bit better than average
Regarding the new syllabus, the sciences mark schemes are entirely different and based more on explaining rather than solving, so it is not directly comparable.