Well, taking a look at the astronomical cost of higher tier spells and also noticing how we have item enchantments with spell cost reduction instead of spell damage increase, it's more than clear that Bethesda wants mages to pay each time less for their spells, but not increase their damage too much. They knew people would eventually stack spell cost reduction items to the point of casting spells by free, thus eliminating the resource management, but at the same time not allowing spells to grow in damage. This is the decision they made regarding offensive magic in their game, and we can't contest that.
However, the problem is: While a destruction mage can be effective in Skyrim, this is not the kind of mage I like to play. I bet many people feel like this too. I like playing mages with amazing power, but limited resources. Not mages with average power and almost no resource management. I want to feel overwhelmingly powerful when I have the resources, but helpless when out of mana. I believe this is the main issue why people are complaining about destruction magic, while some others enjoy this play style. It's just a question of taste. Dual casting firebolts to stunlock a dragon during 10 minutes is effective, of course, and many people like it, but for sure it's not the mage I want to play, and I bet many people agree with me.
In my case, I'm playing an archer for now, which is my second preferred toon in RPGs (after a powerful mage). But the good thing is that mods are just around the corner, so we'll certaily see spell scaling soon enough for people who enjoy overpowered resource restricted wizards like myself
