I would think that they would be good on the street for tread wear and still have some high void areas for the mud, but a guy has to wonder is they would tend to side track in some situations with one half the tire being grippy and being directional the grip side would be on the same side for all the tires. Just my $.02
Directionals aren't new
Geolandars and X-terrains have been around for quite a while, and kuhmo kl-71 have been around for a while as well.
I haven't ran a set but the kuhmo but they look like they'd be decent off road, not sure if they'd have enough contact on road to get decent wear though.