Well, comparing her to iris, she has half the attack, so i'd assume that her attack is her heal amount, but both have +108 from affection, right?
215*2=430 vs 390, but with affection its: 323*2=646 vs 498, so a bit over 3/4 the heal but to two units. Three when shes awakened, so like 215*3 = 645, 323*3 = 969. She also apparently has higher attack speed too, but her range is like 220 vs 260 though she is 5 points cheaper then iris. Seems decent.
What about Mikoto? Good black unit or nah?