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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The collectors armour set apparently means "on no account let this player pick up any motes at all, we must get them all first" given my experience wearing it with randoms.