Maybe sunfire works this way specifically on drow only? (You know, the sun...)
Mind flayers are best handled by a bunch of skeleton warriors...
(You know, skeleton warriors actually ignore magic resistance.... they couldn't care less)
I never soloed a sorcerer so far, but some time ago I experienced the situation anyway... some Improved Mind Flayers (along with two accompanying Umber pets) most unpolitely teleported on Kelsey who was too far away from the party to get real help from someone.
So I had him cast Timestop, Death Spell (good for the Umber Hulks)... and then went "doh".
What do I do now? How am I supposed to actually kill those guys?
Summon things looked the only likely answer!