Blizzard is again experimenting with balance changes in Overwatch, and it's launching a new PTR update to enlist players' help in testing them. This latest patch deals with three characters specifically, not including Hanzo or Symmetra, who were recently highlighted as being in line for some adjustments.
In terms of what is in the patch, Mei receives some significant buffs. The duration of her freeze ability has been increased from 1 second to 1.5 seconds, which Blizzard hopes will better provide her with the ability to take on speedy enemies in particular. Additionally, the alt-fire on her weapon is gaining a few additional shots to provide her with more opportunities to pull off a headshot. In the developer video update below, director Jeff Kaplan explains that Blizzard thinks Mei is close to being balanced but believe she "could use some help," hence the buffs.
Next up is Sombra, who will no longer charge up her Ultimate through hacked health packs. She'll now primarily earn her Ultimate by dealing damage, and some unspecified changes have been made to her weapon as a result. Her Translocator's duration has also been extended, giving her more time to act before it expires.
More importantly, her Hack ability now takes less time to use, and it affects enemies in some new ways. This varies from character to character--when hacked, Genji loses the ability to double jump, while Pharah can't use her hover jets. Kaplan describes this as an experiment; it's not confirmed that these effects will make it into the live game, and it's possible that others could also be impacted by Hack.
Finally, Doomfist's weapon will now recover ammo much more quickly than before. This change actually briefly went live as part of the recent live game update by mistake, but it has since been rolled back.
Overwatch players on PC can check out the changes that are currently in testing on the PTR. There's no word on when these changes will make it to the live game on PC, PS4, or Xbox One, but bear in mind that these adjustments could be tweaked further or eliminated altogether. In the meantime, everyone can take part in the new Lunar New Year event, which introduces a variety of new Year of the Dog skins and cosmetics.