About the best thing the Shoshone get after the early game is a strikeforce of no-move-cost ranged units. You can reasonably expect to get 2, but I have 3 or 4 in my current game (huge map = more huts/land), and happened to find Mt. Kilimanjaro fairly early, so they all have Altitude Training as well (+10% combat on hills, double move over hills). They are sick, usually able to move 3 squares and sometimes 4. I have almost all the CSs as allies from doing far-flung quests, and they can accomplish some really broken combat maneuvers. I am playing a very expansive style (8 cities, all over 10 pop), and they are excellent for reinforcing borders to prevent an attack or to beat back encroaching barbs trying to mess up my development. They also got me 2nd Pantheon, 1st religion, 4 or so pop, an early 20 culture, and a tech or two.
I think the best way to take advantage of these qualities is to go liberty and expand aggressively, fighting defensive wars if necessary and grabbing up enough luxes to keep expanding. At some point I would switch to horsemen or knights for defense/barb missions and try to get my bowfinders some real (war-time) xp. I think opening honor, taking lib up to either free settler or settler+worker, and then going for +50% xp before finishing lib could work well. I took patronage because I wasn't sure what my win condition was going to be and I had a lot of cities and there were a lot of maritime CSs. Obviously rationalism wins games and after that either Order or Autocracy work well.
As far as a nerf, why? Native tongue is essentially a gimmick that forces you to over-produce super-expensive scouts, as some people mentioned earlier. 2 Pathfinders is not enough, so you delay your early development in order to get specific boosts in development. Maybe. Or you get surrounded by AIs. Or water. Or barbs (if your pathfinders have to fight barbs, they're not getting huts). I would say in order to make full use of Shoshone, you need to have at least 2 bowfinders fairly early, and probably 3 is where it starts to get good. Which I think amounts to between 6 to 8 huts minimum (though I could be wrong on that). Those specific development bumps are significant in the short term (pantheon lets you better plan your later cities based on tile/improvement boosts, culture lets you get your barb slaying on quicker, more efficiently, and for more benefit, population lets you work that copper hill to pay for your CBs and build more quickly). I think the Shoshone are powerful, but in order to make the best use of their synergies, limited to a very specific kind of gameplay, best suited to war. As many have noted, it is much more difficult in BNW to keep early conflicts local (i.e. without long-term diplomatic penalties), unless you can goad the AI into attacking you first.
I feel like the AI plays the shoshone this way, which is very vexing to a human player (losing good early city spots to aggressive expansion with no recourse but a diplomatically damaging and difficult war due to BNW mechanics and +20% combat in friendly territory). This is probably the reason people are asking for a nerf. This is mostly a matter of the Shoshone being experts in taking up space and not because of bowfinders, which I doubt the AI can even use effectively. I also doubt that the AI is as good at finding huts or that they can leverage those bonuses as effectively as a human player. My suggestion is for players to expand more aggressively against the shoshone when spawning near them to make sure they get the cities and resources they need. Later in the game they have no ability to get ahead, and my guess is that the worst they can do is stunt a human player's growth enough to let another more powerful AI get ahead.