That is not entirely true. As a union it is pretty influential when dealing with larger issues and has a pretty good record in negotiating with governments, getting favourable outcomes, improving conditions and recently, protecting those conditions.
However you are somewhat correct about workload. This comes down to individual workplaces. As a union rep at a large high school I was told I needed to organise a workplace meeting to discuss the issue as a staff. However the other three union reps are part of the 'management' team and either go along with decisions that increase our workload or actively make decisions that increase our workload. Speaking up about the workload issues gets you labelled a 'whinger'. I still organised the meeting without them. Half the staff present expressed concerns over increasing workloads. There was no real outcome except that any new programs or whatever that may increase workload would be 'discussed as a staff' which they never are.
In the end I gave up. I just refuse to complete any extra paper work I deem ineffective, repetitious or something I've already done but in a more efficient manner that WORKS for me.
My advice to your family members is firstly speak directly with the principal about their issues maybe they could work something out, you'd be surprised how removed some administration is from the work involved in the classroom. Secondly, they could speak to their reps and try and encourage them to organise a workplace meeting. Based on your comment maybe they've already tried to talk to them, if that is the case they should contact their local organiser who could facilitate the meeting. This process would help if a number of other staff contacted the same organiser.
Overall though I think increasing workload is something the QTU is trying to do something about. We have had district meetings about it and filled in surveys. Eventually something may change. But ultimately it is the whole system. Regional directors are under pressure to improve 'data' and this travels down hill. This pressure comes from the DG Dr Waterson who has just been reappointed.
Finally, bit of a rant but to others who may be thinking 'Wait fuckwit isn't it your job to improve student outcomes? Isn't this a good thing?' It IS a good thing but the issue is the way in which that improvement is achieved. Instead of making real, long lasting changes we are 'shaping' data to show improvement. An example of this is putting students who fail on 'Individual Curriculum Plans' and assess them at a year or two below their current year. That way they pass. That way we can say 'hey look all our grade passed this subject' and that, in some cases, gives the school access to some 'Great results' funding (which btw is significantly less than the funding from GONSKI, instead of millions its thousands.)
tl;dr just a whinging fuckwit and union cunt.