We get free Crit % (Raw Crit %, not rating) from leather (and often mail). It's not just leather/mail either, it's any AGI based item, take a look at Betrayer of Humanity stats, or Runeblade of Demonstratable Power, both AGI based items.
They all have 3 rating type stats, AGI and STA. One of the rating type stats is generally always AP, often times one other is Crit Rating and then usually in BiS it's something like Exp/ArP/Hit or something else we like. The Crit from the AGI is free. If we didnt have that, the AGI items would give AP + 2 stats, just like the STR items do.