​This perk is not functioning correctly, as when using Auspex, if many enemies pass through and then exit the Auspex area, they are not counted. It seems as though all 20 enemies need to be present simultaneously within the circle for it to activate; otherwise, it does not work. A test was performed at the Operation Decapitation bridge where the Hive Tyrant stands. I used Auspex on one of the two bridges where numerous killable Hormagaunts were approaching. Since I had zero equipment, the perk should have triggered and regenerated 1 equipment because a large number of Hormagaunts passed through the Auspex area (as you know, during that phase, a significant amount of mobs cross that bridge).

This mechanic does not make sense, especially considering another perk description, "Expert Timing: Enemies marked by Auspex Scan take an additional 100% Damage, but the mark’s Duration is reduced by 4 seconds (base: 8)." This clearly implies that NPCs passing through the Auspex area are marked for a few seconds before the effect fades. Therefore, with that large number of mobs crossing the bridge, between those inside the bubble and those just exiting it, it should have easily reached the 20-unit threshold necessary to trigger the ability and return 1 equipment.

In my opinion, this is a bug. If, however, this behavior is intentional, it should be clearly specified that the 20 enemies must remain within the bubble and not leave for it to work.