Think you will find the re-routing of Qantas Europe flights via DXB killed PER-SIN. Said it before, that the number of passengers using Singapore as a one and only destination is small. Don't have the figures but it was under 25%. The rest are in direct transit or using Singapore as a stopover to somewhere else. This in turn means Qantas is left flighting for the point to point traffic, with a small amount of transit owing to their limited onwards connections, especially compared to SQ.
A very rudimentary way - not including connections ex-SIN through oneworld or Jetstar - may be to compare the previous service capacity with the present one.
Qantas operated the following flights to/via SIN in NS 2007 (see
https://infrastructure.gov.au/aviation/international/pdf/NS_2007_TT_Summary.pdf):
SYD-SIN-LHR (Daily 744) (2,617 seats)
SYD-SIN-FRA (Daily 744) (2,884 seats)
SYD-ADL-SIN (3x weekly 333) (891 seats)
MEL-SIN-LHR (Daily 744) (2,653 seats)
BNE-SIN (Daily 333) (2,079 seats)
PER-SIN (14x weekly 333) (4,158 seats) - appears to have been recorded as 1x daily in seat calculations
PER-DPS-SIN (2x weekly 73H) (336 seats)
Total capacity: 15,618 seats
Presently - including the new PER service - they appear to operate (the split 332/333 operation is confusing!):
SYD-SIN (8x weekly 332, 6x weekly 333) (3,950 seats) (62% of 2007 capacity)
MEL-SIN (2x weekly 332, 5x weekly 333) (2,027 seats) (76% of 2007 capacity)
BNE-SIN (4x weekly 332, 3x weekly 333) (1,975 seats) (95% of 2007 capacity)
PER-SIN (10x weekly 73H) (1,740 seats) (38% of 2007 capacity)
Total capacity: 7,953 seats (51% of 2007 capacity)
Including the cancellation it looks like Perth was disproportionately hit - this may be partly due to Jetstar operating the route which adds another 1,260 seats per week (daily A320).
However if the numbers continue to grow I wonder if that's where the "extra" 332 could go (a daily 332 provides 1,897 seats versus 1,740 seats on a 10x weekly 73H).
Via Singapore would be my pick. Flying over Dubai would be just great. Going back to PER-SIN-LHR would be brilliant.
The new QF77 service arriving in SIN at 21:25 connects well with BA12/BA16. BA11 connects to QF72 on the way back. I'm sure QF would rather put you on an EK plane though!
I wonder if the new QF77/78 will have the suite of codeshares the QF71/72 service has.