Pandaemonium story isn't even full unveiled and the extent of its misery pales, to what you find after a cataclysm or after the Final Days. Their suffering PALES to what you see in, let's say, Ul'dah squalors or a garlean-occupied territory. It's not even a question. If Amauerotian daddy/sensei issues are suffering, sundereds struggles for SURVIVAL are a hell. And you CAN'T pin this on Hydaelyn because said HELL is of their own making (and at times, Ascian making). And that, where Egis and Primals enter. It's not a whim for the sundered as much as you can like to summon old Titan-Egi to die to npcs for you as it is to issue a threat to their selfsame lifes. The games goes for a good while to elaborate how Beast Tribes (or us in Eden) summon primals many times out of despair or necessity.
And you need to read more carefully because I was talking about ATTEMPTS at sacrificing involuntary parties which were TWO, wholly unrelated to the willing sacrifices made before that you mention. One that was thwarted (the 3rd sacrifice) and one that was left as temptative because it was planned to be done AFTER the rejoinings, in order to recover those sacrificed for Zodiark's summoning by sacrificing the remaining inhabitans of the source. And if you don't believe the second one was on the table, I STRONGLY suggest YOU review shadowbringers cutscenes (specifically the one where you finally meet Emet in the Capitol).
And the life span analogy is so absurd that I'll make a point by giving an equally absurd analogy. Amaurotian culture endorses literal suicide whenever someone has finalized his purpose. This philosophy has probably caused the deaths of trillions and trillions of amaurotians who would've lived a bit longer if people conviced there was more to life than a one purpose (just like G'raha conviced the Omicrons shades, shades of a culture MORE advanced than amaurotians).
As someone who is into the field of Biology and research, I can tell you that scientist do not take lives as willy nilly as media would assert. For a long time, there are strict ethics regarding animal use and it's heavily emphasized to make the most of animals, along with making they live in decent conditions and are granted painless and quick deaths. They don't puke and cry for every mice or rat that is killed but they're not nearly as whimsical as Elpis researchers are.