Talent Calculator - World of Warcraft
you dont have 20% more dmg done from behind, but if you crit with both mutliate attacks, it will be the same, highest crit i have done with crappy gear (veterans boots, bunch of blues, whispering blade main hand, ceds carver offhand) is 1.4k with both, thats 2.8k all together, this was also while he was in kidney shot (as it shows in the talent point 9% more dmg while in kidney shot)