About the Us After the Final Boss of Heavensward (Spoilers)

[Alberel]

From what I gather he's not concerned about the state of the world (in that sense), but that our power is threatening their mission. It's basically him freaking out (stoically) that we killed Igeyorhm and (indirectly) Lahabrea, as well as the ridiculously powerful King Thordan and his Knights Twelve. We are tipping the scales, but that's not what he's directly worried about.

That would entirely depend on what Elidibus' mission actually is. It's clear that he believes he is working in the best interests of existence, going so far as to suggest we would share his ideals if we understood the truth of the situation. Considering that most of the ascians (besides Lahabrea and Elidibus) came from another world it is clear that Hydaelyn is not the sole source of life. Lahabrea has heavily implied in the past that Hydaelyn is leeching her aether from somewhere as well. With those facts in mind I'm willing to entertain the possibility that the ascians are actually fighting for a just cause: the survival of whatever Hydaelyn is getting her power from.

If Elidibus' objective is to save something/somewhere from destruction (possibly at the cost of Hydaelyn's life) then an imbalance that threatens to destroy everything would indeed jeopardize his mission.

[Cilia]

If Elidibus' objective is to save something/somewhere from destruction (possibly at the cost of Hydaelyn's life) then an imbalance that threatens to destroy everything would indeed jeopardize his mission.

Elidibus' objective is the same as the other Ascians: to resurrect Zodiark. What that means, how he intends to do so, and what will happen if he succeeds... we don't know.