Instructions
Keep away from the troll. Most of his attacks are melee-range only and will miss wildly as long as you are not in the area.
Strike the troll with ranged attacks and area-effect attacks. This will allow you to do damage without having to get close enough for him to strike you.
Roll away from the troll every time he gets close. This should keep you away from the gravestones he swings at you.
Jump over the shockwave generated by the troll's "ground pound" attack, then return to slapping him with your strongest ranged attacks.