Simple. Once you get the first tier active for the set the perk makes you a magnet to nearby motes, allowing the collector to not have to compete with non collectors for motes or having to run over the same motes 5times before they pickup.
Thoughts?
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I might be more inclined if the perk was an AoE for YOUR kills. If you're close enough then it collects the motes dropped by combatants you kill before some random can slide in & scoop up their ill-gotten gains.