I just want to clarify Critical Vulnerability:
Critical Vulnerability is a debuff on the enemy, not a buff to your character. This means that it does not take into consideration your stats to modify it. It adds the flat crit chance after all other crit chance calculations.
In a given situation, if you have 10% base crit chance, and 100% increased chance to critically strike, and are striking an enemy which has ten stacks of Critical Vulnerability on it, Your resulting crit chance would be 40%.