I tend to just circle strafe them, as they dont seem particularly agile. I use a war axe/shield combo, so I power bash and generally whack the shit out of them. They hate fire too.
Why are you guys even using companions? They are irritating gimps who get in the way all the time. I make them wait at the door of the dungeon and use them as mules.
How did you guys deal with the frost troll? I ended up having to cheat a bit, stood on a ledge where he couldn't get me and hit him with a two handed sword repeatedly.
I bet you'll now say I should have used a companion