I feel like if you want the Trinity changed then the DF would have to search based on a lenient check of certain sums of sub-roles expected to be able to clear the content, and for our current to trinity to actually have more, not less, overlap available to it. Our current "support", which is nothing more than TP/MP refresh (when you consider than casters will commonly require the occasional Foes just to keep up with the melees' single-target dps in a given fight), does not constitute a significant enough divergence from "DPS". They are little more than DPS with attached raid-batteries that commonly go without any necessary use.
I'm personally of the opinion that, unless you're going into deep waters, support jobs really should by no means be absolutely necessary, but at the same time what they do offer shouldn't be so limited. As it stands, their primary benefit is only seen in fights that run long without breaks and require extensive healing (i.e. they should be able to offer more choices, or a variant more universally beneficial, than just Foes, in order to better warrant their presence outside of especially resource-draining fights), or a caster-heavy composition.
But at that point we wouldn't be stuck in a meta that centers almost entirely on Tank & Spank, or as near as possible as we can approach to it, and would likely have a game too difficult much of the fabled DF to handle, even if we managed to assemble their groups quickly and effectively.
tldr; the Trinity will only be changed up in any real sense when people become less dependent on the aspect central to it - narrowed personal responsibility, and "support" is far too thin an aspect of its encompassing roles to warrant its own category due to fundamental design choices in the game. I am not saying that it needs to be a separate role to be a significant aspect of gameplay for "support" jobs. I'm saying the game needs to have more than can be and its players need know what to do with those aspects if they are to be balanced, enjoyable, and significant.