When the troll comes in, fierce attack him, when he swings after
you attack him, jump back. repeat this until the cut scene shows
your character hopping onto a ledge. the troll will have a chain
that he whips at you. stand behind a column and charge up your
arrow/ax until it stops charging, when the troll swings his
chain and it gets stuck in the column, he will pull it out
destroying the column and giving you a perfect shot at him.
repeat this until he dies.