If we're the Ascian/ancient who summoned Hydaelyn, we and all her summoners are in all likehihood also tempered. It was never implied Zodiark would only do that work if he had sacrifices, but that they were necessary to repair the dire state of the world. The final sacrifice they envisioned was to bring back those who gave their lives to summon him and repair the world. It's all well and good noting what it'd take to restore Zodiark and their world, but the Sundering is what made such actions necessary... they don't consider life forms that post-date it as 1) equivalent to them and 2) legitimate. Any warring was a consequence of her being summoned at that point. If the summoning was instigated, as some speculate, against the Convocation's wish to more tightly regulate the world given the way Creation magicks were manipulated into almost bringing about the end of the world (for reasons we still don't know), the misgivings about their misuse becomes something of a wash. Destruction of the world would not follow from her destruction at that point - simply reclamation of aether.
I also find it bizarre that it's claimed that she hasn't lied. Elidibus - when speaking to himself - notes that obscuring your broken state and origins was the intended consequence of her summoning. Is he "lying" or telling half-truths in a monologue? Or is hers just a "white lie" and thus not a real one? The events so far seem pretty consistent with what he said on the matter and she is lying one way or another.
Although there may have been understandable motives to her summoning, and in both cases they were last resorts to extreme events, the Sundering seems like a sledgehammer approach.