I've pretty much spent the majority of the battle with dragons healing myself. Sprinkle a couple perks in restoration so you can heal with less magica, and combine the healing spells in each hand. Not sure if elemental spells mean anything, but I've used a frost shout on a fire dragon to good effect. Its hard to avoid their breath when they're on the ground; but when they're strafing you, if you sprint out of they way u can avoid around half of the fire damage.