how do you kill the rock in dragon age 2?

Question

how do you kill that rock boss in dragon age II?

Answer 1

when its about to do its special attack then go take cover then keep attacking again after it finishes 

see here for walkthrough:

Dragon Age 2 Deep Roads Expedition Walkthrough

Answer 2

you can change the level to "Casual" while fighting it in the gameplay options if its too hard