I think one of the biggest problems with the argument here is that Dale is consistently focusing on whether something is "effective". While others might be looking to argue that something is more or less "efficient".

Effective - producing a decided, decisive, or desired effect <an effective policy>

Now if we're talking about whether or not a job has the capability to produce the desired results, well now we're going to have to look at what the desired result actually is. For some people it's simply to win and in this case any kind of damage output or whatever will work including tactics like DOT kiting. Hence any job can be considered effective. For others the objective of winning is essentially guaranteed as most content is mind numbingly easy so the only real issue is speeding things up to make farming more "efficient".

Efficient - productive of desired effects; especially : productive without waste <an efficient worker>

This is where the real contention should lie. If you go back and compare a Red Mage to a Black Mage when it comes to damage output of spells vs. MP cost. Well, Black Mage is going to win, not only do they have superior increases to overall damage through equipment they also have a more potent MAB job trait (2 more levels of it in fact). We can spin this for any DD as well. While a PLD may in fact be able to deal damage and "effectively" kill and/or tank whatever prey it attacks, a stronger DD (say MNK, WAR, etc.) will undoubtedly be able to do it faster due to increased TP phase dmg/ws dmg/native traits/JAs.

Can a PLD deal damage? Yes
Can a PLD deal more damage and faster than other DD jobs? Most likely not.
Can a RDM nuke? Yes
Can a RDM do more dmg and kill faster than a BLM would? Definitely not.

In summation, PLD + WHM duo can effectively kill off an NM. MNK + WHM duo can kill that NM more efficiently by using the same resources and getting the job done considerably quicker.

P.S. An easier comparison for spell efficiency - Red Mage does 800 dmg Blizzard IV, Black Mage casts the same spell for 1500 dmg. Assuming no conserve MP procs obviously the BLM is more "efficient" because he is using the same MP/spell and doing considerably more DMG. It would take the blm 20 casts to kill a monster with 30k HP and 37.5 casts for a RDM to kill that same monster assuming the same damage occurred on every cast. (Variances in dmg should not change this much unless these spells are resisted heavily and often)