It's not even efficiency. It's people who are too stupid to do anything but specific cookie-cutter tactics on fights. Like a couple months back where I was doing Avatar D fights with a party doing PLD RNG RNG WHM BRD COR. It was taking 20-25 minutes to clear the things. I convinced them to let me switch to DNC/RUN, and we started clearing in 5-10 minutes. Then the RNGs went THF and we were not only clearing faster, but getting much better loot out of it, too.
You start with "it's not even efficiency" but then you write a long description of how you got a party to vastly increase it's efficiency. Wat?

Personally I'm happy to use any combination of party members that can beat the fight. I care little for the amount of time taken per run (as long as we don't time out or almost time out). I feel like a lot of people have forgotten how to have fun.