Oh, is it possible to fight FOEs that early? I just beat the first dungeon and after all of the hype that surrounded them in-game it didn't even occur to me to try fighting one. I assumed I'd have to come back for them in the endgame or something.
It largely depends on your strategy. I've noticed most centrally that FOEs have a
shitload of HP in this game, and early on that's a crapload of SP to spend on healing which you don't have.
Poison is stupid good though among other things. For the first stratum ones and the first one on the second stratum their actual damage doesn't seem
that severe (although someone with the Taunt+Def Boost self skill is recommended for the second's big attack because it could oneshot someone). It's just a matter of being able to pump out enough damage to actually kill them before you're out of resources.
Still, as I mentioned, compared to the EO games the FOEs in PQ respawn the moment you leave the labyrinth (instead of staying dead for two weeks) so it's still not ideal to just pick fights with them at random, as you're likely using a Goho-M after them because you're burned out on resources.
For the record, you get some great stuff from them. The FOEs in the first stratum (specifically the painter? I'm not sure
how different the painter vs non-painter ones are) gave me access to an armor that was well over twice as strong as anything else you can find in the first stratum. Also they hand you personas that are like ~8 levels above anything else you can get from enemies in the area, regardless of what your MC's level is.