I recommend you not to attack at all as mage, it's way too easy to get aggro and die that way. When I did pit on Ironman I didn't use any wand/staff at all, only for last hit sometimes.
It's more efficient to use companion and summon to kill them, you will need lot of potions for that (scrolls also useful). It takes a while, but is more safe.
High level enemies you have to attack, but make sure to kill the small one first, they are crazy fast and can kill you in a blink of an eye