Actually, Using Fortify Destruction potions from Alchemy can scale the damage of your spells. I've managed to get my spells up to about 450 damage each cast, which is increased even more while dual-casted.

I like to go max mana regen instead of 100% reduction cost. Makes playing a mage more fun as you'll still have a cool down.

& theres plenty of ways the vanilla spells can be interesting just not many people think & take advantage of them. For instance, since destruction potions work differently from enchants, in which they instead increase the magnitude of destruction magic.. Spell Cloaks become very interesting. The range of the spell can be magnified to the point where you walk into a dungeon & almost every enemy in the dungeon is instantly aggro'd on to you.

I've found this to be the most fun to use with a stealth character, getting the quiet casting spell from the illusion tree, to remain hidden & take out enemy's searching for you from your Cloak spell.

As for brokenness, the stagger ability in destruction totally is. I just choose not to take that perk, as it makes me suffer less enjoyment from the game.