Other dangers in the Ancient's time

[Cleretic]

I think a useful factor to recall is that tempering is functionally very similar to void corruption. There were probably various forms of aetheric corruption floating around, they just probably didn't do as much as the cases we're more familiar with; much like how Zodiark tempered the Ascians but not to a degree we saw from Ifrit and Lakshmi, it was probably just causing issues like heatstroke and hypothermia rather than total transformations. Still not great, still something you'd want to protect against, but not as bad as 'turn into a brainwashed sea monster'.

As for what threats are out there... well, yeah; these were a people that looked at a behemoth and went 'yes, this is something that would benefit the world by putting it out into nature'; OBVIOUSLY there's nasty stuff out there. We also have a small sample size of dangers Azem dealt with in the Lodestone short stories; the famous volcano of course, but in the Watcher's story he mentions rampaging animals, a dangerous monster made by a child, and poisonous plants, as well as a less 'living' threat of perilous mountain peaks. That's a decent sample size to show that when it comes to the world outside the cities, things aren't too different from what we'd recognize, the only difference is... well, that Ancients specifically looked at half those things and agreed the world was better with them.

We also know of at least six different styles of combat the Ancients partook in thanks to Ktisis Hyperborea (Venat's DNC, WHM and PLD equivalents, Emet's BLM and DRK parallels, Hyth's psuedo-BRD). That's a wide enough swathe to reason that either people were diverse enough to use different organized combat styles, or that threats were diverse enough to warrant diversifying responses to them.