I have a huge supply of super magic potions so mana wasting is not an issue.
are much more effective than health / mana potions.
Do you have Aura of Command, to cast on her death knight? If you drink a shadow potion and wait until the Blind spell wears off, you can attack her. Try starting off with something which can prevent her from re-casting it, Blind her first, or Curse/Freeze. I don't know what her fire resistance is, but Meteorstrike has a stunning effect and can be cast almost continuously.
Also, you can use area effect spells which do not need a target to do damage while you are blind or under the effects of the shadow potion, such as Elemental Hail, Poison Cloud, Hell Spikes...
