Years ago, I bought the miniture Clear-vue Cyclone (made of clear plexiglass) that is the exact same size as the one you mentioned.... in fact Clear Vue had to stop making theirs because of copyright infringements
..... Anyway, it does a GREAT job of separating the bigger bits of woodchips and sawdust, and your shop vac would be virutally clean of that stuff (at least till your container for the miniture cyclone got full). The very fine dust that doesn't get separated will just clog up your filter on the shop vac, and assuming that you only use it for sanding and smaller stuff, I don't know how much it will help with what you are trying to avoid, since the sanders primarily just make fine dust.
If you are using to clean around the shop, all the shavings and cutoff dust from the tablesaw and what-not, it would probably do that real well. Depends on how much you do of the two different activities.
I don't know if this helps..... This has been my experience, though. I never regreted buying mine, but it did take up more space than I had anticipated. You have to run a hose from the shop vac to the dust deputy, and then from the deputy to the device or area you want to use it, and then you have to have a container that the DD dumps into, and that takes up space.