With a single stage, the cleanliness of the filter is a possibly significant factor in airflow. If you have not cleaned it regularly, you should probably try that. I put a super dust deputy on my "2hp" HF and have it exhausting outside so it will not degrade. I was a little surprised to measure only about 500 CFM at the end of a short length of 5 inch pipe and about 400 CFM inside my SS where it is necked down to 4 inch. HF is not at all top of the line but the airflow of your system may be similar - although 6 inch piping should help a little. But if your filter is dirty, you could have even less airflow than my HF.
While my measured (by a cheap meter of unknown accuracy) is unimpressive, the dust collection on my SS is by my estimate good. On cuts where the blade is inside the workpiece, nearly nothing escapes and when cutting the edge of the workpiece so the blade is exposed, it is a lot less than when I was using a shop vac.