Folks are only just now starting to beat AS4. Right now, beating that requires bleeding-edge performance by all participants; anything that can squeeze out another drop of damage is used. We've seen stuff like that before, with book-thumping SCHs and SMNs auto-attacking for the few scraps of additional damage they contribute. Now that it's been beaten, though, time, practice, and additional gear drops will ease these strict requirements, and jobs (PLD in this case) that were out of favor will start returning to the fight.

Alexander was DRK's chance to shine, which makes sense since this expansion added DRK to the mix. Now, if all future envelope-pushing content in the future continues to favor DRK over PLD, we might have an issue, but I think it's fair to have an event or two where PLD is not the darling.

As long as there's variance of any kind between jobs, you're going to see this kind of favoritism emerge whenever any content pushes the envelope of what players can accomplish. The only way to ensure that all jobs are equally powerful in all situations is to make them all exactly the same.