Yes, predestination is one factor. Another is what it takes to become “nonredeemable.” Essentially, it depends on how the soteriology in Azeroth works.
If they have no concept of the afterlife, I don’t think that line of reasoning would work at all.
Even if they do have a concept of the afterlife, it still depends on the soteriology to determine whether an external “savior” is needed or whether something else is required. That’s why, without more information on this, Lilithia’s argument doesn’t necessarily apply to Azeroth.