What I find the most ridiculous about this idea of Lucian really being all noble is that what seemed to set him off on the path to genocide was that the gods eat the souls of dead people.

I just totally fail to understand what the problem is.

Okay, the gods are eating dead souls. And what, exactly would happen to these dead souls otherwise, if uneaten? From what I recall of what the Hall of Echoes is as described in lore, it's a place where the souls of the dead have their memories and identities consumed slowly over time as they merge back into the plane. ...I'm not really seeing the key difference in the fate of the souls.