darkvision should be 60 foot (18m) (at least in 5E) which is somewhat less than the normal range of a shortbow ...that said, I think it is perfectly legit to lose your advantage if you can't see far enough. How can you pick out an accurate spot to strike if you can't really see it? That's when you would create a light source near the target e.g. dancing lights (well that should work!). There is also superior dark vision - both a spell and a natural ability for some creatures, which extends your range to 120 ft...so those creatures/npcs should gain benefit from that over a run-of-the-mill dark vision. I think there are other issues with sneak attack though - it definitely does not always work when your rogue is attacking a creature with allies right next to it. They need to fix this, sneak attack is the rogues bread and butter, at least from a combat perspective (which seems to be all people really care about). I actually preferred 3E/Pathfinder rule where you could only sneak attack with a ranged weapon within 30 foot. That seemed sensible - you had to be close enough to really see what was going on.
