Cordelia is tactless, but helpful in Buffy, not a villian, she actually becomes a celestial being in Angel. Her lack of tact I think is a nod to the Shakespearean Cordelia who doesn't lie to garner her fathers affections.
Echo wastes away because of her love of Narcissus, who doesn't drown but stares into a pool at his reflection until he becomes a flower.
I also like the name Juno.