Zodiark's Codex entry what do we think about it?

[Iscah]

I felt the exact opposite. They sacrificed themselves to power a primal. Sacrificing yourselves isn't really sacrificing yourselves if you are still there. Thus the third sacrifice was an attempt to bring back the dead by using Zodiark's power to reconstruct/rez them from nonexistence. Which never works well (look at Eda. Or Bahamut). I thought they were enacting that plan as a result of tempering and were ultimately just unknowingly serving Zodiark more aether in an endless cycle. Cus they were tempered and that's generally what a primal's tempered do. As of 5.5, we had zero reason to believe a "resurrect the dead" plan would actually work, especially when those dead had been blendered into pure aether to power up a primal enough to stabilize a planet.

This. As far as we knew, their souls were either long gone back to the aetherial sea or destroyed to fuel the summoning. That's why the worldwide sacrifice was such a grave and noble undertaking, not just a temporary "stand here for a while and hold the aetherial fort until we can let you out again". Include that escape clause as in inherent part of the plan and it stops being a sacrifice and turns into just being a duty.

The apparent tragedy of Emet-Selch and presumably all the Ascians as of 5.X, was that they were fixated on this plan that if they just gathered enough aether they could undo the sacrifice and restore their brethren, when really it was a false hope all along.