@Xelnath -- What happened to scaling?
Tristana and Karthus have very few favorable matchups -- especially in this meta. Still, that used to be part of the plan. "Lose lane, win game." These are two champions who were heavily featured in Season 3 all the way to the end, and now they're all but forgotten, despite both seeing some minor buffs in Season 4.
More, the entire plan of playing a champion that had a slightly weaker early game with the intention of outscaling has fallen completely out of favor. Kog'Maw is gone, despite seeing some Riot love. Ryze has been driven out of mid lane. Even Vayne doesn't show up much anymore.
Champions who used to focus on scaling have adapted their builds for the mid-game. That's why you see Twitch building Blade of the Ruined King now instead of Infinity Edge or The Bloodthirster. That's why you see Nidalee rushing Athene's Unholy Grail instead of Tear of the Goddess.
More, the lane bully tanks like Renekton and Shyvana have taken over a top lane that used to be about either DPS champions like Jayce, Elise and Kennen, or more late-game tanks like Malphite and Shen. What HAPPENED?
The massive complain-fest about Athene's Unholy Grail is sort of connected to this, I think. Champions who rush Tear of the Goddess and Rod of Ages are seeing fewer games, and more importantly, they're not making it to late game.
I think the new gold gain items for Jungle and Support have shifted the game's emphasis much more into the mid game than before. Your reworking of gold in this game has been effective in making Support and Jungle roles more influential, but it had the (likely unintended) consequence of making the mid game arrive earlier and become more important. Teams are grouping earlier because the Jungler is ready to leave his jungle sooner, and champions who aren't ready to have a high impact around that time are simply not effective enough anymore.
If I'm right, this is why the impact of an (unfed) AD carry has gone down, and why scaling mid laners and late-game tops have fallen out of favor. This is why it's become so difficult to choose a late-game champion, build for late game, and reach late game.
If that's the case... can you fix it?