For me these are all not so much examples of hints but of instances that just retroactively make sense. As someone said before it's good that they created a concept that you can integrate into the story of the previous expansions so that it doesn't feel entirely out of place.
But I wouldn't really consider it hints in the sense that the story (subtly) directs your attention towards the future reveal of Dynamis *while* you play the story that comes before EW.
So to me, the direction of hints is "forwards" (even if you miss them or they are purposefully hart to spot) whereas Dynamis' integration now that it reveals only works "backwards" for me.
For example, it is certainly interesting that you can now explain the Limit Break as an expression of Dynamis but nothing about the Limit Break while playing the old game indicates to me that it ever could be anything else than aether + game mechanics (because we need a big ultimate team based attack).
Never did I once get the impression that the story (subtly) implies the Limit Break is an open question that could point to something new in the future.
To me it was the power of our collective aether because aether could explain it well enough already:
Aether also reacts to emotions and thoughts. Our soul is literally created from aether. Emotions and thoughts are the very expression of our soul/our consciousness. Memories (and fake memories) are aether manifestations as explained by the old elezen scholar and even Amon, who said the memories of That Day in Elpis have been edged so deeply into their aether/their soul that Kairos couldn't overwrite it forever. And lastly, magic is based on aether and magic is a manifestation of our will and thoughts/what we create in our head. That is literally the foundation of creation magic.
This is also why I thought this whole "Dynamis is moved by emotion and thoughts" attempt of an explanation felt too short and not all that satisfying to me because just as Y'shtola says, aether can pretty much fulfill the same function (but in a "magic-physically" different way).
Lastly, there is also a potential flaw/oversight here (but maybe a lore expert can correct me):
In the boss fight with Elidibus, when he turns into the First Warrior of Light, he literally casts four Limit Breaks against us, one of which we have to answer with our own Limit Break.
But he is both an unsundered Ascian and if I remember correctly he is also still a primal, which is a manifestation of pure aether.
(And the WoL he turns into is ALSO summoned, I believe? So he might be like...a double primal now. But even if I remember this incorrectly the two points before, Ascian + Primal (Heart of Zodiark), still stand.)
So, all in all, he shouldn't be able to cast a Limit Break if it's a manifestation of Dynamis.
Perhaps you could argue that all the souls of the other WoLs he summons are sundered and cast the big Limit Break for him but that still makes little sense to me, because:
A) It's still him who casts it himself. You could argue that he channeled their Dynamis but as a being of pure aether he shouldn't be able to channel and subsequently wield their Dynamis at all (or at least not to this level of proficiency). His massive aether should shield him from their Dynamis and also make perceiving and controlling it too hard or impossible.
B) He casts more LBs (LB1, LB2 and LB3) later on, while also saying "My soul knows no surrender" and the screen reads "the Warrior of Light tanscends his limits". During these moments no other WoL souls are present.
And if he has absorbed them at that point in the fight it would still not make sense to me because what primals absorb is aether. Even if sundered beings have less aether than unsundered ones, if you add a lot of "little" aether you will eventually have "a lot" of aether again.
So if even a being of pure aether can explicitly cast Limit Breaks in an incredibly important and thus memorable story fight I don't really agree that the Limit Break's nature has been a hint all along (and retconning it as a manifestation of Dynamis might not even make sense retroactively either).
For this reason I agree with OP. I think its reveal was very sudden and considering the importance and grand scale of this force it felt very rushed to me, even though I do like the concept of Dynamis itself.
I wish they would have taken more time to establish it by properly hinting at it earlier.
Or they could have saved the Dynamis story line for the second season of FF14 and close the first season with a story purely focused on Zodiark and Hydaelin.
(Although I still did enjoy EW so it's not like I think it was a trainwreck or anything. Separating these two storylines might just have been even better than what we have gotten.)
Because I think Meteion's story itself could be scaled up so much that it comprises at least a whole expansion on its own and not just two zones.