Which job seems the most 'relevant' to the main storyline?

[Enkidoh]

Now, I'm not saying the following because I'm a PLD, but because it was something that I found a bit weird when replaying that scene while being on another job and I think that it can add to the discussion:

In the scene after the fight with Lahabrea at the end of Praetorium, when we get teleported with him to the void, we hear Hydaelyn telling us something like "If thou would pierce the shadows, make thy a blade of light". Now, in that context, a blade would usually be a sword, and there's just a single class/job that can use them currently. Not to mention that while I was on that other job I found the slash animation a bit out of place.

However, I think that that might just be an oversight. As far as I'm concerned, each class/job has its own reasons to be considered "the most relevant".

That's just a metaphor for the Warriors of Light - it's not referring to any particular weapon type at all, but simply the power the adventurer wields.

It directly relates to a prophecy Louisoix mentioned in his journal, that Square Enix revealed on the old Lodestone a year ago, about mankind having to trust in either 'a blade forged in light' or 'a blade forged in might', as shown here (it's listed at the bottom of the page in Yoshi's 'New Year's Greeting'):



The 'blade of might' part of that prophecy incidentally Y'shtola later mentions as referring to Gaius and the Garlean Empire. So yeah, it's just a metaphor for the power of the Echo that the player holds as Hydaelyn's champion, and doesn't correspond to an actual specific weapon type.

I suppose my question would be this: Need there be a "canon job" or "protagonist"?

Well, I guess if you count the five characters shown in the End of an Era trailer, and 'Derplander' specifically, as 'canon Jobs', then WAR would be the canon one, as he's shown constantly in artwork and propaganda as one, dressed in WAR AF and wielding the WAR relic weapon Bravura. But again, those characters are not necessarily 'canon' - they're just symbolic of the player - like a 'insert your character's Job and appearance here' sort of thing.