That's not an easy answer. Typically in RPG's, you have variables such as; Talents, Skills, Bonuses etc.
Often you will find there are 4 different main damages;
- damage + skill damage
- damage + crit skill damage
- crit damage + skill damage
- crit damage + crit skill damage
When you consider that talents in Dragon Age: Origins often affect bonuses and modify the multipliers on damage, there isn't really an answer that I could give you.
You will find with something like World of Warcraft, the critical damage is scaled near a 150-200% increase in damage of the original damage. However, for Dragon Age: Origins there is not really any kind of accurate answer that I could give you.