We have tested, re-tested, and even showed the proof in a different thread. Sword Mastery affects Sword and Dagger at the same time. Like sTIMPZ said, you are going to want to go, at the least, a 2:1:1 builds because your P.Defense will be lower than a Strength Guardian (Rohan Gold). That and you will have to be more focused on Strength than Dexterity.
With a base of, say 180, Dexterity you will still critical hit just as hard as a Dexterity Guardian in Rohan. So the rest of the stat points should go into Strength and Vitality. Reason you will end up still criticaling as hard as a Dexterity build is because of the Melee Force you have. Even if you started out with 20 normal hits on a target, cause of your Melee Force + OS, you can actually build up that damage, along with your critical damage.
We have observed our character going from +20 normal hits to +200 normal hits during OS + CS against Dragon Sages. With 200-400 critical hit as the base crit, to 1.4k as the maximum crit we will hit either before we die, or they die. That is without a Melee Attack + Critical Sword and Dagger, and only using Critical Aura Leve5 (Rohan Crone).