I'll just get to the point, basically, through all of this, i was able to make fortify destruction potions that improve the damage by 168%, couple with augmented shock, the shock dragon priest mask from DB which provides a certain bonus, the master lightning storm spell is able to do 376 points of damage PER SECOND. That is just ridiculous, if this is coupled with a few fortify destruction enchants, this can be cast for very long periods of time.
It just completely flattens everything, even on master. The firestorm spell does damage well in excess of 400 points (haven't tested with fire mask from DB).
Even all the mundane spells end up dishing out ridiculous amounts of damage. Thunderbolt does 301 points of damage per cast. Combine this with dual cast, 2.2x, thats about 662 points of damage per dual cast.
Seriously, i admit that it's self reliant on the player using and levelling and perking quite a difficult and time consuming tree, and it does require the player to constantly make potions, but the end result is fantastic.
PLUS for me it adds a sense of progression, i actually feel like a mighty wizard for once. It's required a lot of time and effort, but it feels worth it, shooting dragons out of the sky in mere seconds.
TLDR: Destrution becomes seriously powerful when combined with alchemy, and the correct perks/gear. (Although it may still be lagging behind the level of power weapon-wielders can achieve). Just thought i'd share.