As for micromanagement, I had a lot more of it with my Warriors and Assassins, with timing power attacks, blocks, sneaking into position for backstabs, etc. My Mage just walks into a dungeon, drops his summons and spams Thunderbolts. If anything gets close (rare, but happens) a FusRoDah clears that right up. Ancient Dragons aren't a problem. In fact, Dragons are a pushover. First time they hover above me, I can just stunlock them and drop them to 10%-0% HP in one go, then they crash, either dead or just needing a bit of finishing off.
You only quoted the last paragraph of my post, but I'll assume you read the whole thing. I suggest you try the advice I listed there, you might be suprised by your Mage after you get him some decent gear and Perks. I found the game to be easier with him than with any of my other characters.