Why is this whole critical strike topic coming up again, hasn't this been discussed like 3 times this month.
Critical Strike Sources don't add, but they do work together.
General Formula
Crit Chance = 100 - (100 - CSama) * (100 - CSbarb) * (100 - DSequip) * (100 - critMonStats)
critMonStats = 0 for characters
critMonStats = 5 for Act 5 mercs & Monsters - if this part triggers: elemental damage and Spells will also be doubled; if an Act 5 merc crits through Ama CS / Barb Mastery or Deadly Strike elemental damage is not doubled.