Deagle is OP? Fixed. Movement was better in BF3? Fixed. Something about netcode? Fixed. The latest patch for Battlefield 4 lists almost 200 fixes and tweaks, including some of the biggest complaints that have come from players in the past year.
Battlefield 4 has had an abundance of problems since it was launched last year, and DICE, the game's developer, has been working on stabilizing the game ever since. In May, they announced the Community Test Environment, which allowed fans to play on servers running versions of the game with experimental fixes. The game's latest patch has fixed and tweaked a ton of bugs and game options, including issues raised by the community.