Berseker/Reaver worked greatly together, if you choose well the talents (the upgrade to barrage that reduced the damage taken is pointless in this build). Though it was useless against the Arishok.
Everything was useless against the Arishok...except kitting.
I once spend many minutes bringing his health down just for him to drink a potion and be right back up. I got tired of that and reduced the difficulty so my bow rogue could actually kill him (and the cutscene showed a dagger-rogue doing the job, lol).
I need to replay the game with a warrior to see how it goes, it's my least favorite DA class by far and it's strange, because I usually play warriors in my cRPGs. I really loved the mage in DAO and DA2, but the class specializations for DAI have me a bit meh. The rogue looks to be the most interesting right now.