I run away dual casting the continuous heal spell.
While people may say that is the coward's way, I have to admit that can be a very fun way to play the game, especially when faced with a high level enemy as a low level character yourself. I think of that as being a survivalist and realistic approach, except for the whole magical healing part of course.
I remember once running away from a dragon as a low level character, and it chased me but eventually started a fight with a giant and was killed. I was then able to run back to the dragon's corpse, absorb its soul, and make off with some valuable dragon bones and scales to sell at the marketplace, while the Giant continued his slow journey through the wilderness all jolly-like. I only wish I could show that Giant some kind of gratitude, but your know how they are.
I also remember running frantically away from Krosis the dragon priest when I first encountered him, carefully dodging his one-hit-kill icicle spells and sprinting away until the combat music faded away and I was no longer being pursued. Needless to say, I later returned armed to the teeth to kill that vile lich.
With my latest character, I just have the incinerate spell in each hand and blast my enemies away before they can fight back. It really doesn't seem fair, but my character does what he must to ensure his own survival. Mithrandir the Altmer wizard doesn't take chances. Occasionally Mithrandir's aim is off and innocent bystanders get caught in the crossfire, but Mithrandir takes no pity on them for having bad artificial intelligence.