But does the shop vac filter gets full of fine dust fast..
Are you asking that as a question? Here's what I've found. I have a shop vac connected to my radial arm saw. It collects the dust from a small box at the rear of the fence where most of the dust gets driven toward the dust port by the blade's rotation. That shop vac filter does get a lot of fine dust, but I don't have to empty it all that often, every 2 weeks or so. It seems to work fairly well even when the filter is full of dust.
I ALSO have a smaller shop vac sitting on top of the table connected to the 1 1/4" dust port on the RAS guard. These two shop vacs together get darn near all the dust that saw makes.
See at the rear of the blade where the dust has built up slightly?
A table saw would be quite different unless it has the blade surround under the table. The whole cabinet area would not direct as much dust to the shop vac and therefore the filter would not get as clogged as fast. The shop vac would be trying to extract the airborne dust floating around in the cabinet rather than directly discharged dust.... not as efficient.
My large Jet 1 1/2 HP DC is routed to collect dust from under the saw's sealed off bottom. There are still gaps under the table and cabinet and the holes for the tilt and height adjustments which I cover with magnetic sign material to seal them off. It does NOT get all the dust and I'm not sure why. I covered the motor opening on the side of the cabinet and even with the mag material on the other openings, I don't understand why there is not more dust collected. My saw does NOT have a blade surround under the table and that would make a huge improvement.
Someday .... when I get around to it .... I may try modifying a blade guard like this myself... I donno?
My shop is dedicated for wood working, so there is some small amounts dust just about everywhere on horizontal surfaces or directly under the saws on the floor.
Dust collection is just about as much "luck of the draw" as actual science in my opinion. Not every solution works for every situation, since machines vary in construction and have different types and locations of dust ports.