I was thinking that Rip picked may have people who were about to die. Weren't most in life-or-death situations? Cold and Heat were running from the cops, Firestorm was in firing flames in a chemical factor, Atom was on a mission, Sara was getting into a fight, (can't remember the deal with the Hawks). Granted, it would be coincidence if they all were about to die at the same time, but given the time travel element, maybe they were at different points in 2016 or thereabouts. That would explain why they didn't make a blip in the historical timeline.