The first numbers, 27,75,105, are the numbers the game displays when I go into TAB/magic and scroll over the spells, not calculated by me.
On this character, I got AoT after impact.
Do you perhaps have any mods on? If not, something must be bugged, because, as far as I've known, Impact does not affect damage.
Argh. If I wasn't currently running through the DB quest for the first time ever, I'd drop my character and re-build a Dunmer evoker.
ResidentPianist, can you describe a typical dragon battle with your mage? I love reading some good after-action reports!
Note that I'm only level 21 or 22 with this character, so I'm not at my peak yet, but here's how it's been.
I start out with a few Lightningbolt spells before the dragon does a breath attack just to ensure that it doesn't resist, since there's a 50/50 chance it uses fire or frost. I endure its first breath attack, either shrugging it off if it's fire (since I'm a Dunmer) or chugging a Resist Frost potion if it's frost (since those ingredients are so common and I always have a bunch with me). Obviously, Restore Health/Magicka potions as necessary, and I also tend to have abundant Regenerate Magicka and Fortify Healthy/Magicka potions, which is awesome. Also, perhaps now's a good time to note that I'm working with 300 base magicka and the rest of my points are going into health, which I think now has a 120 base or so. An Adept Hood, a ring, and an Amulet of Dibella (I think) bring me up to 390 magicka and 130 health.
After its breath attack, I switch to the appropriate element (they're 50% resistant to their element of choice and 25% weak to the opposite), generally using Apprentice spells--Adept spells can be somewhat expensive at my level (though I can afford to fire off a few), and Ice Spike travels much faster than Ice Storm (not to mention that it doesn't freakin'
dissipate in the wind).
I may dualcast to stagger the dragon during its shout, or use Fus Ro to interrupt it (no use in using the third word; just extra cooldown), but it's generally easier to fire off one spell in each hand since it costs less and I'm more likely to hit; whether I dualcast really depends on what's going on in the battle. Some dragons at my level, particularly Blood Dragons, can give me a hard time, so a +50% Destruction potion and a few Adept spells usually brings down their health fast.
When they're on the ground, I try to keep combat at a medium distance so that I can use gouts. A dualcasted gout with a potion bonus can be especially powerful, and the range is just long enough for me to keep it up if they try to escape into the air. I keep a Staff of Flames with me just in case (haven't found a stronger staff yet), and it has helped a lot.
If I can sneak up on a dragon, Marked for Death followed by a quick, dualcasted, potion-enhanced spell can deal a lot of damage, especially if, by chance, I use the element the dragon is weak to (remember, you only know if you're fighting a Frost Dragon or if the dragon already used a breath attack). If the dragon is 50% resistant to the spell, the ambush is rather lackluster, but damage is damage, amirite?
Currently, I'm pretty sure I'm playing on Expert. I changed it to that ages ago for my Khajiit, and the difficulty carries over to other files, but I'd have to check to be sure. Either way, it could be no lower than Adept.
With mid-level mages, I usually rely on Apprentice spells for primary damage and Adept spells for burst damage or necessary AOE. With higher-level mages, I rely on a mix of Expert/Adept spells (since Expert spells don't have much in the way of AOE, which means I have to go back to being accurate), throwing out Master spells when useful or necessary. A stealthy Firestorm can work wonders if you've managed to sneak into the middle of a Forsworn camp

Master spells almost always require planning to use, though (because if they didn't, you may as well use other spells), and when you
do use them, it can make a big difference. Become Ethereal, Ice Form, Fus Ro Dah and Whirlwind Sprint can help you prepare for them. Many, many other magics can help open up an opportunity, to, but I won't list all the options.