Level 12 Derth Mage

Hail all,
I am having trouble progressing. I noticed against melee and ranged enemies I usually can handle them with my spells, but against other spellcasters I am having a hard time fighting them. My Magic resistance is as high as you can get it (85% I think?) and the spells I get hit with still do a lot of damage to me. I am currently trying to fight the Witch Queen and these witches are getting on my nerves even with my high magic resist and resist poison wands. Any help would be appreciated!
I am having trouble progressing. I noticed against melee and ranged enemies I usually can handle them with my spells, but against other spellcasters I am having a hard time fighting them. My Magic resistance is as high as you can get it (85% I think?) and the spells I get hit with still do a lot of damage to me. I am currently trying to fight the Witch Queen and these witches are getting on my nerves even with my high magic resist and resist poison wands. Any help would be appreciated!