When I realized that "oh yeah, if I hold forward and power attack, I'll dash ahead like a mother******" battling mages became easier. When you're actually close enough to hit them some more then time a shield/weapon bash whenever they go to cast a spell. --- "So watching Xenosaga is horrible, but watching Fei sit his ass around in a chair and tell stories all Disc 2 is okay?" - DivineDragoonKain
Although magic doesn't scale for the player, it seems to for enemies. This is perhaps why mages tend to be the most difficult enemies you face in the game. There are some things that can help.
If you're a breton, you'll be taking a quarter off all the damage they cause automatically. Against boss mages, you should activate Dragonskin and constantly heal with one hand. You'll never run out of magicka when facing a mage with spell absorption. Taking damage from only half of all magical hits and constant healing makes fighting mages trivially easy, but only once a day.
If you're a nord, then just hope the mage uses frost. Frost attacks are by far the most common form of magic enemies use. If things get too hairy, scream a Battlecry at the mage and beat on him as he runs away.
If you're another race, things will be harder. The Lord and Atronach stones can help a lot when fighting mages. Do a quest for the temple in Riften and you'll get Agent of Mara for a free passive 15% magic resistance. The Magic Resistance and Atronach perks in the Alteration perk tree can help too. Enchanting is also a good option. Boots can have elemental resistance and rings, amulets, and shields can be enchanted to resist magic.
I'm having trouble with them as well, playing exclusively melee. Just recently someone was using some frost spell that would get bigger as it advanced towards me. So basically if i get close I have no time to evade it, if I'm far it becomes so big I can't evade it. It also got 90% of my health on 1 hit lol.
I ate more than my own body weight in food for healing on that battle.
Also using 2-handers makes it even worse. If you want to use a ward or heal, then you lose time unsheathing the weapon when you're right next to it. I'm hoping for a "unsheathe weapons faster" mod, lol.