A contractor saw is the worst for dust collection...
There's just too many open areas on a contractor saw and most table saws unless they have a shroud around the blade. My Bosch 4100-09 has a blade shroud with a rear 2 1/2 shop vac port and it works real well. My other Craftsman motorized saws have a steel close off that seals the bottom which I made with a 4" dust port center, and that does not work at that well. Some of the air borne dust thrown off the blade will go down the port, but a lot of it settles in the cabinet's corners and gets sort of an "aerodynamic" sculpted shape.
You would need a HUGE volume of moving air to get all the dust and your DD just won't do that. It's better for hand held tools sanders etc, and maybe for a router table, but it's no match for the table saw. I also have a Craftsman hybrid, an enclosed cabinet saw where there is a sloped platform leading to the 4" dust collector port, and that design is somewhat better, but there is still dust in the corners. :frown2:
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)