What about the beast tribes? Some of them were certainly not tempered, like the Stormblood tribes for obvious reasons, but in particular a couple of the ARR tribes appears unlikely to not have been tempered. I mean the Ixal and Amal'jaa tribes.

The Amal'jaa seem to be very zealous about exposing *everyone* to offer up their souls to Ifrit, as shown by the Ifrit questline. To them, servitude is not enough. All must subject themselves to Ifrit, hence how they forced the treacherous merchant and brass blades to Ifrits tempering. Knowing this it feels unlikely that the beast tribe Amal'jaa have avoided tempering.

As for the Ixal, Sezul speaks about Garuda very knowingly, as if he and his Ehcatl Nine have witnessed her. Also, knowing Garudas personality it seems unlikely that she wouldn't have made the entire Ixal race into slaves.

In addition to all of this, of all the ARR beast tribes I'm fairly certain the Ehcatl Nine are the only ones to confirm they have actually renounced their god. In fact if I recall correctly the Silphs have a cautious respect for Ramuh, and Novvs Clutch admits to still worship Leviathan, though its true the Little Solace Silphs haven't been tempered, as that is part of their plot, and Leviathan, as well as Titan, doesn't seem nearly as interested in making servants as Garuda, nor are the Sahagin or the Kobolds as zealous as the Amal'jaa, so that makes it less likely that Novvs Clutch or the 789th order have ever been exposed.

Odds are high, however, that the Amal'jaa and Ixal have been tempered before, and if they have, then that would suggest tempering is not necessarily permanent as the people of Eorzea believe, as the Ehcatl Nine in particular renounce Garuda openly.

Really, there are a lot of unknowns about primals. It may be possible that having your faith shaken enough might remove the effects of tempering, just shaking someone's faith is much easier said than done. Having your world be slowly consumed by the same Light you worked in service of because you did everything it told you to do, however... I imagine that would be sufficient to shake the faith of the Firsts Warriors of Light.