This skill is automatically acquired at level 22.
The Burglar Tools Minor Legacy Increased Range for Reveal Weakness increases the range of this skill by up to 20 meters.
You should always put this skill on the Raid-assist-target of your fellowship. When soloing, it's not always necessary to use the skill (as normal mobs drop quickly).
The effect of this skill will stack on your enemy, so if you're not the only burglar in the fellowship/raid... stack this skill!!