What ballpark range do you need to be to take Shadow Empress down

Easiest way is to bring somebody that can bind, then with whatever damage range and how fast you can kill you just leave about 15% of her hp or something and just spam away at her while she's still binded. She cannot heal at all when binded.

This is what I've been doing with a friend on a mule DS and it works fine. If you're worried about not having enough DPS I would just go this route to be safe.