You do have to wonder what is going on or wrong at QFi. These delays have been happening for weeks now and I have not seen anything like it. I wonder whether it is a crewing minimal time on ground issue?
I am not a QFi 'insider' but if you're referring to QF25 delays, that seems to be due to the much smaller time with the newish timetable for turnarounds, rather than the aircraft from Sydney spending all day in Japan.
With other routes, yes, crewing problems must be some of the reasons: for instance if 'the 1' runs badly late, the next '1' for the Singapore to London sector may be delayed, with it and 'the 2' further complicated by how the flight crew are (as one would expect) based in Australia but the cabin crew are normally UK residents.
QFi hasn't publicised this but perhaps they have a shortage of available 'qualified running staff' i.e. international flight deck crew, as any late running may have a compounding effect, with some staff insufficiently rested (or perhaps having already worked their maximum permitted hours for a month?)
The key question is 'how come the vast majority of QFi's international airline competitors who aren't based in Oz can manage this, while QFi cannot?'
JQ has just admitted its performance 'hasn't been good enough.'
Yet QFi continues on its most major routes to have unacceptable delays, and less frequently, cancellations. Businessmen and women who for instance have recently assumed that QF93 would get them from Melbourne to the 'City of Angels' as per the timetable have been left high and dry on some days. Yet they're often paying sky-high fares.