R/D suffers from the lack of a decent non-energy attack, so a lot of the time you'll just be sitting there twiddling your thumbs or healing (lol) yourself for kicks. It's easily the worst rogue combo available, though it's probably viable just for PvP due to the fact that it is a rogue.
D/R has nothing to help with heals, and its dark damage elites are pretty much useless, as the dark damage buff to increase the dark damage skills is less than the earth damage passive all druids get. In short, Earth Arrow will always do more damage than PWE, until they decide to buff it.
If you're not looking to play a healer, I'd suggest a caster with a healer secondary (M/P, M/D, maybe Wl/P). D/R won't keep up with damage at all in PvE and won't be able to heal any high end instances. If you have your sights set on rogue, R/S and R/Wd are both good for PvE and PvP.