I think that Qantas has got this one right.
To me it makes no sense to operate three diferent SYD-LHR flights with a choice of refulling in Singapore, Bangkok or Hong Kong. If you are going straight through to London why would you care where the plane bounces ?. Having all the traffic funneled through Singapore must give Qantas staffing/purchasing savings as well as extra flexibility when something goes wrong.
So - from a Qantas perspective connections in BKK/HKG are a non issue - if you are going to London you do so via Singapore. This leaves only traffic with a final destination of BKK/HKG on those flights. If I want to do a stopover in either of those cities then I dont really care about the connection time.