The only issue with Acheron and Firefly, as I've used both of them too, is that setting up a near infinite loop with either requires more work through Blessings/Curios to pull off while Feixiao's natural synergies make an infinite loop require a lot less work, even at E0, which in her case the Blessings/Curios just gives higher damage potency and loop consistency.
I mean, Firefly does this almost every time, too.
Or any properly strong Erudition/Acheron.
Still, feels good, no?
The only issue with Acheron and Firefly, as I've used both of them too, is that setting up a near infinite loop with either requires more work through Blessings/Curios to pull off while Feixiao's natural synergies make an infinite loop require a lot less work, even at E0, which in her case the Blessings/Curios just gives higher damage potency and loop consistency.