Let's play a game: Save the Ancients!

[Cleretic]

And yet it was a victory nonetheless. Were it a war with a litany of casualties, what would you say then? Were it... dare I say, a form of pandemic created by a malevolent entity, what would you say then?

I would call ANY situation where victory requires sacrificing half your population, on top of the people who died anyway, pyrrhic at best, no matter what you were going up against. I think that's especially true of Zodiark; both what we saw and heard about in the aftermath shows that it was an absolutely miserable victory. They won, but at terrible cost. (Also, I feel like you're trying to imply something without saying it with your examples, so maybe you should try saying what you mean.)

And again, to bring back the original point: all of this was caused, by one man, by accident, while trying to answer a pretty worthwhile question. I don't think Hermes being some unparalleled genius actually matters here, because he didn't even mean to do it. If you want to get an idea a similar situation is in the sundered world, I can immediately think of three people who 'caused problems by accident':
-Alphinaud with the Crystal Braves... which was a vastly different situation and still had almost all of its consequences mitigated with little cost (RIP Minfilia and Raubahn's arm),
-Ga Bu, who created an overly emotional Titan... in a context where Titan was going to be summoned anyway
-And Gilgamesh, who created a primal so minor that a lot of people forget that it actually was one

While those are hardly nothing, they are microscopic compared to the impact of Hermes' whoopsie. So yes, I think it's an absolutely fair argument to say that most of the Ancients were stupidly, absurdly powerful.