A380focal:
Wouldn't it be better to compare the 767-400ER with the A330-300 since they have the same range - 5650nm. In which case the A330 caries 10% more passengers for a given config.
The A330-200 has a range of 6700nm - considerably more than the 767.
Airlines usually pick the airplane based on the number of passengers they hope to carryand therefore, an A330-300 carrying the same pax number as a 767-400 will not be more fuel efficient per pax carried than a 767-400.
The A332 has more range than needed on most flights for which the 764 could be used with lower fuel burn.