For the following 3 seconds, damage is not always reduced by 90%; it is now reduced by a maximum of 90%, depending on how much resilience the Rogue has. The damage reduction will be four times the damage reduction resilience causes against critical strikes." The resilience required to reach the 90% damage reduction cap is 22.5% critical strike damage reduction, or 444 resilience.
http://www.wowwiki.com/Cheat_Death_(Rogue_Talent)