Burrito, Sky's comparison is not apples because the 744 is designed to carry more than the 773. The comparison is like comparing a minibus to a sedan both carrying 4 Pax. Sure the minibus will burn more fuel, but things will even out per pax if you fill the available seats.
Now possibly the full 744 will still burn more fuel per ASK than the full 773, because it's an older design. But that's not everything, does the 744 have more premium seats? Do they have premium passengers in them? It's about profit not fuel per ASK. What about freight? What about landing slots? You'd need to run more hulls using 773s. More parking bays, more staff, more airways charges. What about purchase/lease/ownership costs?
The same argument applies to the A380. QF A380s have low seat count because they are a 4-class configuration with a large number of premium seats. ASKs are not applicable here either. Now, if the premium passengers ain't buying tickets then we have a problem. And that has been a big problem with the QF A380s during the GFC. But I think a fully booked (with premium pax) A380 would generate profits a 777 could only dream of.
Not saying QF shouldn't have 777s, they unquestionably should. The fact they don't is a serious management screwup.