The spells follow a similar suit. If a destruction spell does 25 damage in OB, and can be used in conjunction with a 2h weapon or a sword/shield then how will its damage compare in Skyrim where you must equip a spell to use it? This is where the most damage will be lost if spells aren't tweaked in the right manner, because even as a fighter you could just cast your mana bar worth of destruction spells to supplement your damage output.
There are a couple ways to balance it and I am curious as to which Beth has chosen. They could implement an 'off-hand' system where spells or weapons equipped to the off-hand did some % less damage. Or they could just make 2h weapons more than double the damage of a 1h weapon.
Maybe it is just me but it seems like all the roads lead to an increase in player damage with weaponry OR spells and a decrease in player damage with spells AND weaponry.