Hear is a better question: Should bungie introduce the Flood to the destiny paraverse? Given the 9 were able reach across the paraverse and pull items from these other universes, it's theoretically possible that they could accidentally introduce a flood super cell to destiny. It's even possible that the flood had interdimensional travel since halo lore theorized that the flood had escaped the milkyway galaxy and that there could be entire galaxies consumed by flood. This would fit into destiny lore perfectly and could explain a lot of things. For example; what if the Witness knew about the flood and this was why he wanted to rid the universe of all physical life to prevent an outbreak. Or this could explain the vex and their creation, as what of the Gardener and Winnower created the vex as a counter measure for the flood, since they are the perfect anti-flood unit. It's also possible that egregore is a proto flood still in it's early stages of infection. After all both are parasites that keep their hosts alive in a psychological prison while it feeds on them and both can reproduce by spore, not to mention that in halo lore the proto flood would increase aggression in the infected much like those exposed to egregore. This may also explain the rift between the winnower and gardener as they may have different philosophies for dealing with the flood. The gardener could keep creating life hoping that an immune life form would emerge while the winnower believes the best solution it to wipe out life.