Exuvia creates a "Zephyr Machine" that creates a PBAoE ring that increases the skill damage of operatives within it.
When an operative in the ring shoots [and hits] and enemy, the Zephyr Machine gains 1 charge, up to a max of 30 charges.
When an operative in the ring deals skill damage to a target, the Zephyr Machine consumes 2 charges to deal electrical damage, up to a max of every 0.2s.
Like her ultimate, this comes from Enya, and is not an Auxiliary Unit, and hence isn't affected by Auxiliary Unit modifiers.
This skill lasts 20s and has a 5s cooldown, but the cooldown starts when the machine disappears, not when the timer ends, so the default uptime is 80%.
Similarly, lasting 20s then going on cooldown for 5s means its total duration is 25s, which means that since it also costs 25 S-Energy, Enya doesn't need extra S-Energy regen to maintain it indefinitely.
The damage is (72% of Enya's ATK +50), which ideally procs every 2 shot hits
If it procs at its maximum rate of every 0.2s, the machine will add an extra (360% +250) damage per second.
If an operative is shooting less than 10 shots per second, it averages an extra (36% +25) damage per shot.
The Zephyr Machine doesn't get any benefit from an operative shooting more than 10 times per second.
Technically higher fire rates can be useful as they allow you to maintain higher charging rates even if you miss a lot or tend to shoot the terrain a lot, but if you are actually hitting an enemy more often than 10 times per second then the Zephyr Machine doesn't gain any extra benefit from that excess RoF.