This is sort of straying from the subject (and maybe worth a thread of its own but I don't really know what the central 'point' of it would be), but I think that 'dynamis circa Stormblood' is very different to 'auracite circa right now'.
At the time of Stormblood, dynamis (or what would be known as that) is very much an abstract that you're not really supposed to be thinking much about, nor really putting that much stock in at that point; in fact, I'm fairly sure the devs hadn't even come up with dynamis at that point, so it wasn't a thing beyond the general storytelling conceit of 'someone really emotionally invested is gonna fight harder'. So technically there were pieces of this puzzle, but they weren't really being put forward as something to put together rather than just 'ideas that permeate the world'. There's not a lot of equivalents to that right now, since we're very much in a 'wrap up the loose ends before starting a new thing' part of the story, I'd cite examples if they were coming to mind.
Auracite right now is instead similar to Omega in that storyline, and I was going to write up that comparison, but I think the closer comparison point is the Warriors of Darkness in 3.x; they're a concrete thing, we have facts on them, there's a backstory, there's connections to both tangible stuff we're very familiar with (for the WoDs, Hydaelyn and the Ascians; for auracite, the Ancients and particularly Lahabrea) and more abstract stuff that their very story pins down into being more 'real' (for the WoDs, the shards; for Auracite, Ultima, who's now suddenly more than just a random raid boss). We know what we're looking at, we know there are 'real' connections to discuss, and it's definitely planned for the future.
So yeah, I look at auracite now in the same way I looked at the WoDs then. And when I look back at their story in full, I do realize that nothing that went on to be important in their story in Shadowbringers was already independently around in 3.x; everything that was important to them was either newly introduced in Shadowbringers, or already a part of their story back in 3.x. So similarly, I'm very disinclined to believe that the auracite story, whenever we get it and whatever it becomes, is going to suddenly bring in other things that are already independently important right now; I'd scrutinize everything we find after now that looks related, not the stuff before it that they happened to not bring in at the time.
EDIT: And for the record, my read on 'how did Hydaelyn beat Zodiark' was literally just that she was better at fighting. Combat doesn't come down to bashing two power levels together and the higher one wins; hell, the WoL themselves is a testament to that. Some level of subterfuge and sneak attacks like Mikko mentioned might've been relevant and very useful, I'd also point at their actual fights: while there's extra factors going on in both fights that'd mean we weren't seeing how they fought when they fought each other, I do think it's worth noting that Hydaelyn uses a variety of actual complex combat techniques, while Zodiark's combat style is pretty untrained punches and lasers. Which makes sense; Zodiark wasn't created to fight anything, while Hydaelyn was explicitly created to fight Zodiark first and foremost (with a few other jobs in there too).
I don't need an extra reason for why Hydaelyn won that fight: I look at those two and absolutely buy that she'd come out on top.
(I made another point here but it was REALLY tangential so I deleted it)