[Anarchy Nooblet]

Well if your asking the best way to kill a banshee specifically why not come prepared? And on top of that if you have a maxed out inferno, when she starts to summon the little monsters start charging it up but make sure you're far away enough away from her but she's still in its radius. If done correctly, you will kill the little ones and since she's far enough away by the time the spell gets near her she'll be vulnerable and bam, you just killed her AND her minoins in a single shot.