Let's play a game: Save the Ancients!

[LilimoLimomo]

But you're merely assuming here that most Ancients could single-handedly end the world in a way their superiors could not contain, and ignoring that Hermes and Athena were both immensely gifted and near enough the "pinnacle" of their race, if you like, if we accept the premise Amaurot was the intellectual capital of the world, the Convocation the most powerful of them, and that they were considered to be on the same level.

Actually, we are given explicit proof that the Convocation are not determined based on power; Hytholodaeus — who had exceptionally low power outside of his perception — was offered the position of Emet-Selch before Hades, and the only reason he wasn't on the Convocation was because he refused the invitation.

As for the proposal that Hermes is immensely powerful, I don't see anything in the narrative that supports that idea. We're never told that, never shown that. Are we assuming he's powerful because he has a high-ranking position? Again, Hythlodaeus is his boss and outranks him, reminding us that there is no correlation between power and Amaurot's hierarchy.

[Dikatis]

As for the proposal that Hermes is immensely powerful, I don't see anything in the narrative that supports that idea. We're never told that, never shown that. Are we assuming he's powerful because he has a high-ranking position? Again, Hythlodaeus is his boss and outranks him, reminding us that there is no correlation between power and Amaurot's hierarchy.

Well, we do know that the researchers of Elpis come running to him to subdue any creations that are running rampant and he quickly puts them down when needed. In addition, he fought WoL (who would go on to defeat the Keywarders of Pandaemonium, who are all immensely powerful mages recognized by Lahabrea himself), Emet-Selch (Hythlodaeus knows of no mage more powerful despite regularly bumping into the best and brightest of Amaurot), and Venat (a former Azem who once stopped a cataclysmic meteor and more or less laughs off her successor fighting a volcanic eruption turned into a creation). Yes, the security measures of Ktisis Hyperboreia weakened his opponents, but Hermes is not to be trifled with.

[LilimoLimomo]

Well, we do know that the researchers of Elpis come running to him to subdue any creations that are running rampant and he quickly puts them down when needed.

I think you may be misremembering. A researcher does come running to him when the lykaons (muscle-wolves) become violent, but not to ask for his aid, but rather just to let their superior know about the situation; this same researcher lets Hermes know that their colleague will unmake the creatures:

I had just fed them myself, and the okyupetes were keeping a wide berth. It is the nature of the lykaon that is to blame. Their innate viciousness.
Temperament aside, it is an outstanding creation, perfect in form and function.
Though it may not be suited for release, I've no doubt that the bureau will accept its concept for preservation.
In any case, there's no point in postponing the inevitable. Doros will revert them all once the paperwork is in order.

Unsolicited, Hermes interjects himself into the situation because of his distressed feelings about the deaths of these creatures.

Source: https://ffxiv.gamerescape.com/wiki/Aether_to_Aether

In addition, he fought WoL (who would go on to defeat the Keywarders of Pandaemonium, who are all immensely powerful mages recognized by Lahabrea himself), Emet-Selch (Hythlodaeus knows of no mage more powerful despite regularly bumping into the best and brightest of Amaurot), and Venat (a former Azem who once stopped a cataclysmic meteor and more or less laughs off her successor fighting a volcanic eruption turned into a creation). Yes, the security measures of Ktisis Hyperboreia weakened his opponents, but Hermes is not to be trifled with.

If I'm trying to be objective, I don't think this provides us with enough information to move the needle one way or the other. As you mentioned, Ktisis Hyperboreia weakens his opponents, and since we don't know by how much we can't learn much about Hermes' strength from that.

To put it in mathematical terms, what we learn is the inequality:

(EMET + WOL + VENAT)/HYPERBOREIA > HERMES

Since HYPERBOREIA could be any value between 1 and infinity, it doesn't get us any closer to understanding the value of HERMES.

[Dikatis]

Since HYPERBOREIA could be any value between 1 and infinity, it doesn't get us any closer to understanding the value of HERMES.

Hermes repeatedly casts Meteor, referred to by the researchers and WoL as an "apex magic" for an apex predator like a behemoth, throughout the fight. Not to mention other high-level spells like Tornado (a wind spell superior to Aeroga/Aero III) and Double/Quadruple (an ability used by Emet-Selch while staking his life in the Dying Gasp).

There's no reason to believe that Hermes is somehow a weak and inept mage when all signs point to the fact that he's a brilliant mage and creator, hence why he was trained to become the Chief Overseer of Elpis in the first place.

[Iscah]

Double/Quadruple (an ability used by Emet-Selch while staking his life in the Dying Gasp)

That could be key, because he likewise is staking everything on the outcome of this fight.

As for power levels in Ktisis, I suspect it might not be "a fraction of their usual power" but "reduce to a fixed level" (an arbitrary 87, to be exact). Consider that Hythlodaeus – apparently normally far weaker than his companions – is by game mechanics now of similar strength to them. Either the others have been brought close to his natural level, or all four have been weakened even further.

But this conversation is far outside the scope of "can you see a way to save the Ancients?" and is on its way to turning back into the same old argument.

[LilimoLimomo]

Hermes repeatedly casts Meteor, referred to by the researchers and WoL as an "apex magic" for an apex predator like a behemoth, throughout the fight.

I don't think that's an unreasonable interpretation, but my personal reading is that this statement is made in the context of what abilities to give to an animal. The behemoth wasn't created with the intent that it combat Ancients, who have capabilities far superior to it.

There's no reason to believe that Hermes is somehow a weak and inept mage

Oh 100%, I agree that there's no reason to believe that he's weak or inept. But at the same time I haven't seen anything that would lead me to think he's above average from a power standpoint.

when all signs point to the fact that he's a brilliant mage and creator, hence why he was trained to become the Chief Overseer of Elpis in the first place.

Again, Hythlodaeus oversees Hermes, which is strong evidence that magical prowess is unrelated to rank. Hermes is shown to be both knowledgeable and invested in his field of study and its related work, and those are the aspects of him that others hold in high regard during our adventure in Elpis; they do not comment on his power.

[LilimoLimomo]

Dang, you really just said Hythlodaeus=0

LOL it's true I did, but only because I feel that's how my beloved boy would have chosen to represent himself XD