Sure more info would be appreciated in the tribunal from what I have seen (Im still like 1.5k xp off 30, just read these forums alot lately) but theres only so much that can be given.
IMO the biggest issue is the term feeder, its used far too much and far too easily. I am in mid and get 3v1 ganked 3-4 times because there are no MIA calls and they avoid my wards/traps/Im on low health and suddenly Im a feeder, we are all in mid and go to push, Im running up and suddenly its a 5v2 not a 5v5 because only one other person committed and suddenly Im a feeder, I have a bad day or lane against a champion I cant counter with the champ Im playing and suddenly Im a feeder. The term is used far too much, sure there are some people who intentionally feed (6 pairs of boots for example), but people ask everyone in /all chat to report you as a feeder when its legit deaths, its not like you just run up and stand there to die most of the time.
That being said, LoL IS a team game, what Im seeing is low to no kills with deaths and no assists just to push towers. If you play only to back door you are basically setting your team up for a 4v5 all the time, theres little to no way that you arent getting kills/assists in the laning phase if you are actually trying. Especially as Yi as his ultimate is so good for mobility, chasing and escaping and simply DPSing champs down. If you are consistently getting 0 kills and not even trying to take on champs, then yeah, I would say you need to be punished or something. Playing a game just to BD is selfish, you may get alot of towers and maybe even win the game but by doing so you are putting 4 other players at a constant disadvantage, Im assuming letting them die alot and pissing them off, its not fun 4v5ing if someone is AFK, it is even more annoying if its 4v5 because someone wont participate or is off doing their own thing.
Basically, sure BD all you want, but you shouldnt neglect everything else just to do so, its a team game and honestly in 20+ minutes theres no way you arent going to be near a fight of some sort and not get a kill/assist.