I have used a RF-30 size Mill drill for over 20 years and literally thousands of hours, and roughers have a place on this lighter equipment. If you occasionally have to run deep slots or remove a lot of material to hog out a shape, the hog mill will let you move more metal with less stress on the lightweight machine. It makes the whole process faster and less nerve-wracking.
You might not be able to use the tool any where near its limits as others have noted; but it can help increase the limits and productivity of your machine.
One caveat, though: Hog mills are generally cobalt. They will run longer at higher speeds than HSS, _BUT_ they are more brittle than HSS. So they help by reducing stress in a less than completely rigid machine; but, if you push them hard enough to deflect the machine, they are easier to snap (in the small sizes).
smt