It means, "your cold resist, ignoring caps"
So, if you have +165% cold resist in Merciless, but its capped at 75%. your evasion rating is increased by 165%.
People don't use AA because of the mana reservation. The 13% phys DR is amazing. you stand still during every attack...
Phase acro is of course 30% spell dodge. This gives you that, without the 50% penalty to ES/Armor, and 30% penalty to block. Then of course all the passive points to get there.
This is BIS along with Belly and Kaoms.