I don't see that big of a problem with destruction damage. It isn't scaled enough for playing on master unless you want every fight to take forever, but on adept it is fine if you use enchantments to keep cost down. You don't need 0 cost, but some cost reduction is key. My advice is 25% reduction by level 10, 50% by lvl 20, 75% by 30, 90% by 40.
Dual casting expert level spells fully perked is doing around 200 damage per hit. Considering most enemies have 500 health at that level with some in the 1000 ball park(deathlords) you are killing most enemies in 3-5 hits, and if the enemy has a weakness to an element(deathlords don't like fire) it takes less. Figure in that those attacks are staggering your enemy you are set.
I play dead is dead, and I have often complained about destruction damage.... but my two characters who have done the best playing dead is dead are both destruction mages. One died at level 72, and the first time he even saw the "Your health is low" warning was when he was using equilibrium with transmutate to create gold and knowingly dropped his health low. He died because he jumped off a cliff and had recently used a shout so couldn't use ethereal..... The second is my current character, level 34, no problems so far.
The primary advantage to magic is not damage... it is not getting hit. If you don't get hit, you don't take damage, and you don't die. Destruction mages don't have the damage of melee characters or archers, but they are more mobile than both and capable of tying up their enemies to keep the distance. Archers are not very mobile while attacking which leaves them vulnerable if someone gets close. Mages on the other hand can move while casting, and when you figure they aren't wearing armor they can run the fastest if they need to. Now add impact(stagger), conjuration(decoys), and illusion(chaos) and pure mages can go through entire battles without getting hit.
I actually prefer the lower cost rather than damage, which is different that my original position. Right now at level 34 with 85% reduction I can dual cast an expert level spell about 5-6 times doing 1000-1200 damage. Or I can switch to a weaker spell getting a lot more casts and more damage but taking a lot longer to deal that damage(useful against mammoths). If I had to pay full cost I would only be able to dual cast once and at +160% damage(if it was the same as melee & archery) I'm doing 520 damage before I'm out of magic. Basically half the damage I'm currently doing. So now I'm chugging either cost reducing potions or magicka potions all the time.
Sorry... I like it how it is right now

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