Hey man! I'm not exactly an expert on Yi, but here is my advice.
If you are the fed one, it is your job to shot call. People are much more likely to listen to someone who is fed than someone who is weak. Now, that's a tall task in solo queue, but as you climb, most people figure out that they want to win enough to swallow their pride for one game. Now by shot calling, I mean picks, turrets, warding and sweeping, dragon, and baron. Being fed aspect aside, if you are the jungler, baron and dragon are 100% your responsibility. It is your call whether to give a dragon for mid tower or when to make a baron call. Most players accept this at higher elos and this will eventually trickle down into Gold and such because that's how mistakes are prevented and everyone is on the same page.
To the aspect of what you should be doing, look at your team vs. their team early in the game, at least by 10 minutes and ask yourself "Can we win a full 5v5 fight, like the game depends on it?" (Hint hint, it does). If the answer is no, your team should not teamfight unless you have a blatantly obvious advantage. At that point, it's best to establish a 1 - 3 - 1 split push to split their team up or try and freeze lanes so your team can catch up in gold. Also if you decide to split push, ensure that everyone (yes, EVERYONE) wards the absolute crap out of the enemy jungle and river on whatever side you are splitpushing on so that you can see the enemy team when they come and you sre much less likely to get caught and die. Your job as a Yi isn't to join your team in a full fight, you just die that way because people know to kill you quick. Instead, your job is cleanup afterwards, i.e. picking off people walking away with 10% HP or entering a fight after that Morgana ult is down or the Thresh is already dead. If your team doesn't cooperate, then just split push. You won't get anywhere if you team is arguing and getting caught alone or in bad fights.
Just my two cents. Hope this helps! :D
