Due to the LHR curfew, all QFs SIN services arrive late at night - too late for any connections. Thus if going to a whole bunch of secondary Asian cities you fly SQ/MH or someone else to make a same-day connection.
If RedQ actually works it might support some early morning Asian flights out of Aussie ports in addition to the LHR connections.
The lack of daytime departure from LHR has been raised before and is a sore point amongst some travellers. If QF29/30 was maintained as a third daily LHR flight, I think that Qantas could have run QF2 (LHR-SIN-SYD) as a daytime departure. This would allow LHR-SYD pax to retain a night-time departure by using QF30 or QF32.
SQ has three flights per day LHR-SIN; these are spread somewhat evenly across the day at 1100, 1800 and 2200.