You will have to use a silver or magic weapon. If you are still struggling press start go on to settings, game settings difficulty and turn it to the left to make it easier to kill apponants.
u can also use dreamora weps too..
*hits self* of corse, well pointed out.
Also if you don't like taking damage, you could give will-o-the-wisp a couple of swipes and run for a while, drink a potion and go and fight it again. But be careful of the red beam thingy that it fires at you, it takes your health and dose something else (but i forget )
i dont know about health but it drains magicka for me
do a forward power attack on it then just keep doing fast swipes while randomly side-stepping
my guy can kill them in a hit, cause hes awesome