It is often faster to hotfoot it to a new location than scour fallen enemies for specific drops. They really aren't that bad especially in a fireteam of three who are spread out across the map. You need to learn which ones are which so you can abort the lengthier trips. My advice is do any kill and collect missions then use a scan or scout mission to take you to a new location where you repeat the process. Accept and abort any that remain before leaving so they might be kill or collect next time. Also worth mentioning you can rinse any kill and collect missions on a planet and then leave to orbit and back to patrol for a fresh batch. Often quicker than returning to start area. Obviously these are only valid tips for people farming patrol missions for rep gains.