+3, Ransom, as far as I can tell, was marked ridiculously easy (I kind of consider it to be pretty easy to analyse compared to say, Richard III) last year owing to its being a new text. I think part of this is also to do with the fact the examiners' are to a certain extent marking you relative to everyone else who does that text, and most of the state has no idea what to write on a book if there aren't a whole heap of study guides and sample essays for them to prescriptively regurgitate in an exam situation. So doing a new text tends to be doubly rewarding for kids who actually have the brains and diligence to form their own personal opinion about a text. Also as MJRomeo mentioned, they tend to pick the easier prompts first, so that they can eliminate them from the list of possible prompts, before the study guides have time to write a whole heap of sample essays on the obvious prompts.
Contrariwise, when a text has been in circulation for a long time often they purposely choose hard prompts that are designed to negate the advantage provided by stacking up on study guides and sample essays, in order to discriminate between the kids who are simply regurgitating something they read, and the kids who genuinely have an insightful understanding of the text.
I should perhaps add the disclaimer that most of this is more of a theory I have than absolute fact. I obviously don't know VCAA's exact method for picking prompts, but this seems pretty logical to me: aiming to pick prompts which aren't covered by study guides, and doing the easy prompts before the study guides manage to write on them.