Fates literally do not scale.

[Felis]

I did, I did a fate outside Bluefog with 30+ people, then did it with 10 hours later, the exact amount of enemies spawned and they had the exact amount of health. Every fate in this zone has the same number of enemies spawning with 30+ as it does with 10, and the exact same health.

Fates do not scale.

The stats of the enemies scales, not the amount of enemies.
There was an explanation in the beta forum