You do realize that you can reduce the mana cost of the spells to almost nothing right?
The issue I'd say is mana regen in combat being so low. Running out of mana with potions and a high elf with Highborn is nigh impossible though.
Again: a miss and a swing.
The problem is that, unlike other offensive skills, destruction relies on something else to deal its damage.Yeah, a character using 2h perks will need armor to stay alive, but his damage comes from his 2h perks. An archer will need sneak or LA, but his damage will come from his bow and arrows. It can be enhanced with enchanting, but it does not depend on it. You can still shoot arrows even without +% bow damage enchants.
However, that is not the case with destruction. You still need to build defenses, but if you take destruction, you need complementary damage (conjuration) and a high enchanting (cost reduction) just to do your job. Destruction, on its own, is so weak that it forces you to pair it up with very specific perks, which is completely against the entire spirit of the game (freedom of choice).
Both need defensive perks, but only one of those need to rely on 3 different trees for their offense.
EDIT:
10 pages on a subject that's been done to death? No.
From everyone I know they do plenty of damage at high levels with destruction. The argument I see in similar threads is that you don't do the same damage as an exploited warrior with 2 500dmg maces. Well, duh.
Then I am sorry but our interaction is at an end. When you come in a thread without reading it, not only is it rude, but you are not even in a position to contribute because you do not understand what is being discussed. So you come here with generic crap, answering to arguments no one every raised, and otherwise being simply disruptive while not acutally bringing anything.
Reported. Read the thread first next time.