QF are in a bit of a pickle on PER-SIN and I cannot see a way out for them at the moment.
As someone who travels PER-SIN v.v on a 6 to 8 week basis, I am yet to travel on QF since the reintroduction of the route and will not anytime soon.
TZ (and therefore 3K via PBG) slaughter QF on price if you book more than a month or two ahead. SQ slaughter QF on schedule, connection options in Asia and on service and aircraft quality. QF are expensive, have no full service connections in Asia and operate a poor aircraft choice with a poor schedule.
Moving back to an A330 with new J and a better schedule (leave earlier from PER so you have more connection options in SIN to Asia or have the day in SIN) would be a start at least. But they would have to fill it versus the stiff completion on the route.