Okay so I have no clue on what made bungie think this ugly -blam!- anvil head of an exotic was worth even releasing. So let's list off how it works:
1) Reloads Trace rifles over time (Cool mods can already do that so why waste the exotics slot)
2) damaging a boss while the trace rifle and your subclass are the same damage type marks the target and if an ally (So we can't actually use this exotic ourselves) kills the boss they get a heavy brick...
Just to point out Aeons does this better by just finishing elite targets to spawn heavy and majors for special. This doesn't require using a specific subclass or weapon, nor do you need to stop shooting or killing enemies for your friends to kill them for you for it to work. Honestly Bungie what the -blam!- is this absolute trash?