Swapping SYD-SIN-xDOH-JNB (QF, then QR) to SYD-JNB (QF) saved a little over $400 in taxes (on a LONEx) plus returned two segments (*). Ticketed. Cutting out the QR long haul flights was a Good Thing (tm).

*: being used to save an additional $250 on a Peru domestic side trip. So $650 saved which is enough to buy a SYD-SIN return and earn more miles whilst at it. Go figure.