On the Pathfinder forums some years ago (well, over a decade ago, I think), I was involved in a long and not particularly well-mannered discussion about the effectiveness of slings.
The conclusions were (depending on which side of the fence you sat);
1. slings ought to see better stats and better effectiveness because, historically, they were favoured over shortbows in terms of range and effectiveness.
or,
2. slings were not as good as composite longbows so should not be improved.
Okay, which side of the debate I was on might be obvious. The thread is still accessible over at the Pathfinder forums if anyone is interested in trawling through it. It contained a lot of information and references relevant to D&D 5e.
Whips have never really been dealt with properly in RPGs to my knowledge. They can be useful tools and are certainly colourful weapons for the right character archetype and build, but they tend to be lumped in as weapons which do a bit of damage and can occasionally grapple. You would struggle to replicate Indiana Jones, Zorro or Catwoman under most RPG rulesets (D&D 5e included).
