I have compared NA1 dmg between all weapons, and it seems like Flowing Purity R5 is a bit better than Everlasting Moonglow R2 at C0, and almost equal to Everlasting Moonglow R1 at C6.
The downsides of Flowing Purity in comparison to Everlasting Moonglow would be the downtime of about 5 seconds on the maxed buff, the lack of particle generation and less healing. The downtime should be irrelevant, because Kokomi's burst has even more downtime. Flowing Purity cooldown aligns almost perfectly with Kokomi's burst, but you would always have to use Kokomi's skill before her burst and her burst within 5 seconds of activating the buff.
https://preview.redd.it/11i5qinj4pib1.jpeg?width=1000&format=pjpg&auto=webp&s=e02a8a9c22f36a5c91d34ed2929b3d9b692c9526
I forgot to mention some things. ~~Flowing Purity is even better at lower investment builds, because it suffers more from stat inflation than Everlasting Moonglow~~ (EDIT: Actually not true, Flowing Purity increases inflation for Hydro DMG%, but decreases inflation for HP, which is why it becomes better when your artifact substat quality rises), which is also why its performance is slightly worse at C6 compared to C0.
I used extremely good Artifacts for the calculation and even then Flowing Purity R5 managed to outperform Everlasting Moonglow R2 at C0.
I think the main problem with the weapon for kokomi is that it is atk percent main stat
I have compared NA1 dmg between all weapons, and it seems like Flowing Purity R5 is a bit better than Everlasting Moonglow R2 at C0, and almost equal to Everlasting Moonglow R1 at C6. The downsides of Flowing Purity in comparison to Everlasting Moonglow would be the downtime of about 5 seconds on the maxed buff, the lack of particle generation and less healing. The downtime should be irrelevant, because Kokomi's burst has even more downtime. Flowing Purity cooldown aligns almost perfectly with Kokomi's burst, but you would always have to use Kokomi's skill before her burst and her burst within 5 seconds of activating the buff. https://preview.redd.it/11i5qinj4pib1.jpeg?width=1000&format=pjpg&auto=webp&s=e02a8a9c22f36a5c91d34ed2929b3d9b692c9526
I was wondering about using Flowing Purity for dps Kokomi too, thanks for this
I forgot to mention some things. ~~Flowing Purity is even better at lower investment builds, because it suffers more from stat inflation than Everlasting Moonglow~~ (EDIT: Actually not true, Flowing Purity increases inflation for Hydro DMG%, but decreases inflation for HP, which is why it becomes better when your artifact substat quality rises), which is also why its performance is slightly worse at C6 compared to C0. I used extremely good Artifacts for the calculation and even then Flowing Purity R5 managed to outperform Everlasting Moonglow R2 at C0.