of course your QF status is useful on partner airlines!! However just not for upgrades - at least with points (with some unique exceptions). In terms of airlines assessing who to give an op up to in the case of a cabin being oversold, then status CAN influence choices but, to be frank, QF Gold, aka Oneworld Sapphire status, is not that high up the tree (sorry) and, for example, BA will have a slew of it's own high tier members such as Gold Guest List, Gold (oneworld emerald) and so on ahead of other partner airline emeralds and sapphires etc.
However oneworld status such as sapphire is most useful ! It will give you access to partner lounges (ie: BA), in the USA it can give free bags on AA flights, lounge access, and priority boarding and check in (as with most oneworld airlines).
So whilke your chances of an upgrade are very very small (but it never hurts to ask!) your status absolutely is valuable with the partner airlines.
See this page for more information:
Benefits | oneworld