How to kill Baal; mage on impossible

[KongMysen]

With frenzy 3 on a solo stack BK with the splinter cell, even a mage can kill most stacks with just one or two retaliation strikes on each stack. Once the attack stat reaches 100+ that is.

By waiting, you can usually get a chance to slip in and hit Baal even though there are lots of enemy summons. I never feared a loss in my mage game even though there where tons of summons at a time. Evlin, Stone Skin and Calm Rage can get the BK's at close to full strength always.
Only problem is the Arch Demons but Turn Back Time solved this issue for me. Without Turn Back Time, you have to rely on 2xEvlin but it should work almost as well.

I'm not sure why you can't kill fast enough? Maybe you're not wearing the undead leadership items or the Splinter? Or you didn't put points in Frenzy? Either way, try to search the forum for other posts regarding Baal. I think DGDobrev mentioned some way of provoking Baal to do his normal attack instead of the summon.