Some passives, like Twisted Fate, Janna or Zilean's, affect a team globally, hence the name "Global Passives". But their effect is hardly visible, even if many know its effectiveness. Riot therefore believes that passives that offer a lot of power without really adding any interaction need to be modified.
Currently on the PBE, Twisted Fate has a "new" passive. Instead of giving a bonus of 2 gold each time someone in the team kills a unit, each time Twisted Fate, and only him, kills a unit, he will receive between 1 and 6 gold coins. 'gold.
Statikk discussed this change:
Our goal is not to reduce the number of picks, TF brings a cool and unique experience to the game. We're just trying to make it fairer to play against.
Morello, Lead Designer, also did:TF's old passive is basically a lot of power for the whole team, and doesn't add interaction. The new passive doesn't really add more, but at least it guides us towards something more manageable (and more satisfying for TF players). I know it's not much of a problem in SoloQ, but TF needs a nerve. It's literally the best nerf we could do.
The story could have ended there, but it looks like other passives in the genre are concerned, with Morello having discussed Janna's: I'm not sure why we didn't change it, however I predict the players aren't going to like it when we do. Get ready, this passive will eventually be removed from the game.
Due to his popularity in high level competition, TF is one of the characters of the League of Legends considered as OP, today it seems that Riot is working on his subject in order to reduce his power.