So when the 2nd group loads their DKP on the same night- it won't in anyway cancel out or mess up the 1st group's load, right? It should be safe given the people who attended each raid? I know that's a question that may come up
That is correct. Depending on how you set up events in your calendar each run should map to something specific to show who was where and with what group.
lets say on 8/17 you have Raid 1 Kara and Raid 2 Kara. When the raid leaders/officer for raid 1 upload their snapshots from GRSS they will have an option to associate those snapshots to an event. Each set of leaders simply needs to make sure what group they are responsible for so they are associating their uploads to the right events.