I would recommend as many "Steady" gems as possible. They give you health and resilience. You can never have too much resilience as a Warlock. It's the bread and butter defensive stat for PvP, in my opinion.
As a Feral Druid with 31% crit chance and ~2500 attack power, nothing is more frustrating than going up against a Warlock in heavy resilience gear. Instead of critting on every third hit, I only crit on every tenth or so. And for a lot less since resilience also reduces the damage done by crits.
The way I see it, you can never go wrong with resilience. And if someone tells you to get +hit, +penetration and +damage instead, look at it this way: your DPS when waiting for a resurrection is zero (0), no matter how much +damage and +hit you have.
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