Even if they do something with dual weild spells, having to cast 4 seperate spells for a similar effect to what you could get from one cast in previous TES games will svck.
4?
As much as I understood how spells works (correct me if I'm wrong) is that you equip a spell in each hand (we'll say that fire is in right one and shock is in left one, also this is in pure spell user caster scenario) and then, by clicking a left hand key, you cast a lighting bolt, by holding it, you shock enemies in front of you with lighting storm (don't know what command is used to place runes tho).
Anyway, same is with your right (fire) hand, only spells would be fire ones.
Now, if you had fire in both of your hands, when you use both hands at the same time, you should be able to use fire, but with greater effect, but in this case where you have shock in your left and fire in your right hand, when you click both hand keys at the same time, you will cast light spells instead.
Click for casting a bolt of light, hold it for casting a light beam and ? (like I said, I don't know what you have to do in order to create a rune spell) for creating a rune that will make a burst of light when enemies approach it.
Light element would be an advanced element and therefore really strong (awesome damage that will deal both fire and lighting type damage; unless they make special resistances for it; and will also burn mana).
It's great effects are balanced by you having to be good at fire and shock in order to cast it.
Also, that would mean that you would have to cast two spells to get a third effect and not 4.