From a QF Lame's point of view. Flying to Dallas from Sydney, far as I know, it hasn't ever had to stop on the way to get more fuel so you should be fine. However, when flying to Brisbane from Dallas, it does sometimes have to stop via Auckland to get more fuel usually due to strong head winds or expected fog/poor weather in Brisbane.
It depends what time of the year, but I remember a few months back, they always seemed to have a LAME on standby in Auckland ready for the 744ER to divert if it needed to, but at the moment there isn't anyone on standby at Auckland if that suggests anything,