Actually just prior to the 744 ceasing DFW-BNE-SYD it had become more of a DFW-BNE-'anywhere but Sydney' service. (Hence the reason the Qld government were lobbying hard for the DFW-BNE leg to be retained and will be happy with any announcement of an additional Brissy-US destination for the 789.)
Often only a relative few passengers were transit pax for Sydney with most inbound pax terminating in Brissy or transitting to Cairns, Darwin, Perth and all points north and west. Passengers to Sydney were mainly joiners in Brissy who would then transit Sydney for Jo'burg, Jakarta, etc.