Illusion Spells Question

[CalibanX]

So, when you dual wield an Illusion Spell like Fury or Calm or Fear, does the DW version just increase the duration of the Spell or does it allow the spell to work on higher level opponents? Is this how you're supposed to cast Illusion spells on the bosses that often resist the one handed versions of these Spells?

[Guss]

Not sure about duel casting " sure it would increase the time of it " but you need to hit a certain skill requirement/perk to cast on certain creatures. Edited December 6, 2011 by Guss