I'd say the main advantage is domestic frequencies, because say flying into Melbourne from Paris via Perth, when you get to Perth you have at least 7 flights a day to Melbourne and that is just Qantas and that is not including Jetstar. Plus you have connections to other places international airlines tend to skirt like Port Hedland, Adelaide, Hobart, Canberra and many others, turning these destinations into 1 stops, whereas other airlines can't with at least with adding a stop.
Not sure why multiple frequencies are a great advantage. When connecting, only one or two of the frequencies would be relevant.
I agree PER remains a good connection for people travelling on QF coming from ADL but that is more because, up until now, QF has chosen not to offer a service between ADL and SIN. ADL-PER-LHR on QF is no quicker than ADL-SIN-LHR on SQ.
PER-LHR (QF9/10) is not currently an option for pax from HBA or CBR unless the pax want to go via MEL also as the HBA-PER flight has ceased for NW23 and the CBR-PER flight does not connect with the 787's flight times.