DPS means damage pher second, il use that word alot.
When i load my cruisers with my missles and watch what happens missle turrets show fully charged but they dont fire imediately , but rather wait for something. This increases fiering period significantly and reduces DPS. I think turret wont fire untill missle that was fired before from the same turret dont reach its target. This means that the more time you wait for missles to reach their target , or the slower the missles are, and further the target is, the less often do they fire. I can confirm this because when i equip fast missle launcher i do the most DPS, with the same number of ships and missle turrets on them but different type of turret(slower missles) i do noticabely less DPS. With fast missles i can win a mission but with any other missles i cant.
I dont think this is a feature but rather a bug, if its a feature slower misles are vastly inferior to their faster counterparts.