I know this is out of left field, but Corki needs a rework.
Corki at the moment is a midlaner. He is so bad at ADC that he's not even listed as an ADC on op.gg. I understand that Corki isn't good right now and that this could be hard to believe but I think Corki needs scaling nerfs, and base buffs, or something of the sort. I believe that he should get a rework, or atleast a mini one to address some issues.
Corki does way to much damage with his Q. His Q is an AOE bomb that might as well chunk half of a squishy's HP bar. This plus an auto attack means that he's impossible to "trade" with unless you actually go in.
Champions like Twisted Fate, Ryze, and other ranged point and click CC characters just simply can't stun him. By the time they get in range, he has thrown his Q, auto'd and E'd away, so you can't even get your spell in. Even if you do, it'll stun him after the dash ends (Which is another problem in League, similar to Tristana's W), it doesn't feel fun to play against, and it certainly doesn't feel like there are ways to play around it.
Riot tried very hard to make Corki "different," and they succeeded at that, but the champion just isn't fun to play against. The Marksman update just wasn't enough to put this champion in line.
He can burst like an assassin while having the range of a mage. He pulls the same rage out of me that
does, but at least she can't dash away, at least she is gankable.
Corki as a champion can't be stopped late-game. People complain about Vayne's Q crit, while Corki is throwing bombs left and right that deal AOE damage, poking the enemy down, and eventually dashing in and autoing with rapid-fire cannon. The second he has gotten two crit items and Trinity, you can't get close as a squishy. Even if a tank CCs him, you need to worry about the delayed bomb while dashing in.
I feel that Corki's problems go hand and hand with how overpowered Crit is. I think that Crit should be changed to a ramp up system, where every auto after the first would gain some form of damage, or simply make it a non-rng system. Once Corki gets Infinity Edge, he can chunk out over half a squishy's hp.
Despite this, I still feel he is fixable with the current system. I think having his passive be intertwined with crit, could do a big help. Something along the lines of "Building crit further increases the magic damage of Corki's autos," something similar to Jhin and attackspeed.
Finally, I think that keeping both Mid corki and adc corki viable will be the greatest way to go. It'll be hard to do, but if it is done correctly it would make a lot of players happy.
Thank you for looking at this long read, these are my thoughts and feelings on the current corki, as well as what I think we could do to fix it.
Obviously, I am not a riot employee, so I can't guarentee that I am right. I'm just putting my opinion out there.