“From the perspective of the US airline industry, low-cost carriers affiliated with legacy airlines just don't work.”
This may be true but does not mean that Jetstar will go the same way as its American cousins.
Jetstar is a separate business from QF. Overheads and labor costs are totally different to QF. Song, Ted, Metrojet and others in the US suffered as a result of operating within the parent business. None were stand-alone airlines that could negotiate truly competitive labor rates like Jetstar has. And of course, all 3 of the above examples were operated by airlines that employed chapter 11 rulings to achieve the drastically reduced labor costs they were seeking, thus obviating the need for the sibling carrier anyway.
“Nothing Premium over there.”
Make a bet. Have you ever flown Alaska or Virgin America? Much better than QF domestic.