I don't know exactly how, but while fighting SCal, I was unable to see a majority of the hostile projectiles, and died very hard due to invisible bullets. I could see some of the trails if the projectiles had them, but for the most part, I was fighting blind.
I checked everything, upping the particle cap to 10k, tweaked everything else in the video settings, changed weapons, and nothing worked.
Then I decided the Astrageldon Auric set was probably flooding the screen a bit too much for me, and made it hard to see what projectiles DID appear. I shimmered it and crafted the regular set, and all the particles in the fight were back.
I rechecked all the video settings, and no changes would make the projectiles vanish again.
Very puzzling, and also sad because my DPS with the Astrageldon set was way better