Go to any race of significant size and count the number of ultralight carbon tubulars. Some are rebuilt with more spokes, but many are not. Fewer spokes means less mud build-up.

Rim diameters are generaly not any wider than any other road rims, cyclocross tires are usually in the 30 to 35 mm range. Even if they weren't, I've run a 45mm tire on a road rim without issue.

That said, for non-racing purposes I wouldn't want to use a super light wheel for all of my riding, on road or off.

Lightweight road wheels will be fine. I would avoide a cyclocross race tire for the riding you described, however, because their performance is usually mediocre on road, they wear extremely fast, and offer very litle flat protection.

When you say 10% hardpack dirt/general off road, how technical do you mean? If it's just packed dirt roads and the like a 32mm touring tire may be your best choice.