Like all "good"

news stories, two stories intertwine in the article.
First, I'll deal quickly with the "broken belt" excuse at MEL viz. JQ & QF. I believe
QFCSA has alluded to some of the real reasons for the holiday chaos, but the sickie rate and ill-testing and design of systems for resilience against stress scenarios is ridiculous. A few people that should be dragged out into the street and shot, and life moves on.
Now the focus of the topic. Firstly it is probably unlikely that one can predict the weather before a plane can be sold out (or sold to a certain capacity that necessitated this drastic action), and anything can change in a few hours. Admittedly it was probably most undignified that two passengers needed to be involuntarily denied boarding (or offloaded after boarding) due to weight. But what are the alternatives:
- Two volunteers decide to get off the flight. Hopefully they are compensated. Perhaps DJ didn't offer a good deal to sweeten the crowd. Either way, didn't happen, so IDBs were necessary.
- Cancel or delay the flight. Accommodate everyone, find a bigger aircraft or hope the weather gets better. Finding a bigger aircraft is temporally infeasible; hoping the weather gets better to fly is in the hands of the Gods. You could also put pax on other flights that may be able to tolerate landing in such weather (e.g. JQ, or SQ via SIN) - also complicated. In any case, makes the news? Yep.
- Throw off a few more bags and put them on the next flight. Better than removing two pax? Possibly, although some pax will be most annoyed when they arrive in DPS to be told they don't have bags for a night or more. Makes the news? Good chance.
I don't know if DJ have an IDB policy (heck, does any Australian carrier have one? There is an "Overbooking" policy, but this is hardly given at the check-in counter, and this is not an overbooking situation), so under what term in the CoC can they kick off pax in this kind of incident I have no idea. Assuming that a term exists that they can exercise that power, it is usually at their discretion if they must choose someone to involuntarily offload, then they can have any sort of criteria to do so. Or they could just pick names out of a hat. Or they could have a race - one lap around the airport - the last two to finish are kicked off. Just kidding in the last instance. In this case, they've come up with a modest answer - the last two to check-in. No one is happy to be involuntarily denied boarding, but unfortunately it had to come to police coming on board and frog marching them off the aircraft?
A second check of another thread shows that DJ have a set compensation schedule if you are denied boarding, which includes a full credit for the flight you cannot board. Hopefully the two offloaded also have travel insurance, since they'll necessarily need to make arrangements with their accommodation and possibly tour operators in DPS to reaccommodate their involuntarily modified schedule.