How do you kill the Tormented Bosses as Frozen Orb?

I find it kinda funny how I can literally obliterate everything in the game except bosses. Even high level pit bosses take time, but I can still kill them. I tried a tormented boss last night as a overgeared Frozen Orb Sorceress and I didn’t even tickle it.

Help?

Here’s 100+ Pit Frozen Orb.

https://youtu.be/YHidCKSr8x8?feature=shared

What level was that?