Tempering

[Kyan]

I think it also has to do with the nature of the primal as well.

It should be noted that the term "tempering" is specifically for the process that Ifrit carries out on his followers, including Amalj'aa, as you've rightly pointed out, but the community uses as a catch-all for all primals. In relation to Ifrit, for example, there are also Little Ala Mhigans who have been "tempered" and infiltrate the camp as spies to coordinate the capture and smuggling of people. The Amalj'aa, too, are able to have quite cohesive thoughts and plots. I think ultimately, the process of being claimed by a primal makes that person worship said being, and in doing so, that person will go to any ends to make sure their "god" will persist. We only really see the extreme effects of amnesia or psychosis or insanity with people who have been tempered multiple times, or just aren't compatible or strong enough to survive the process.

This claiming process varies from primal to primal, where it changes people's personalities to even their physicality (re: sylph that are touched are purple).

If I were a betting man, I am going to say all reavers are drowned/claimed by Leviathan, because Sahagain aren't native to our lands they need a source of information and communication, as as they are there specifically for breeding to save their population, I doubt they have large numbers. Using human thralls as front lines will certainly save them some casualties.

If we were to look through the eyes of NPCs, it isn't too far of a stretch to think that these touched people are brainless or crazy. They cannot fathom why anyone would independently worship a primal and steal crystals to do so, or hang out with beastmen who are the enemies of the state.