I'm conflicted as fuck about them getting killed off so early.
I wanted to see more of them and see if they'd get developed more as characters. I like villains that operate in a group and have their own personalities, quirks, M.O.s, weapon of choice, tactics, etc. But I guess looking at it like that was wrong to begin with, because they were all raised to be angry killing machines anyway, devoid of any real personality.
I'm guessing Ashi will learn to lament the death of her sisters eventually.