Weapon damage is only one variable in a complex damage calculation. There's also max resource, penetration, CP, crit chance, crit damage modifier, skill rotation, passives, enchants, recovery, procs, and other considerations. Don't get tunnel vision and focus on a single variable or you will reduce your actual damage output.

DKS is not an effective set because there are other ways to get the Major Brutality buff without wasting a 5 pc bonus. Use potions (the Alliance War Stamina pots are a cheap option) or a skill instead.