Definitely use Shock against dragons. A flying creature that gets struck with lightning either dies or stops flying; then I can just start use poisons to weaken them even further (for example, weakness to fire... or shock) plus enchanted daggers and shouts (try the ice shout). (Note Class: "Sneaky Gandalf").
Shock plus posion (weakness, Parylisis, Ebonyskin & Dragonhide) plus magicka immunity plus magicka regeneration at 250% gives you a dead Alduin on expert.
