Now that the changes from the latest patch have settled, let's take a look at some of the biggest winners and losers.
Last season, Amumu's Q was buffed to have 2 charges instead of 1. This made him such a strong pick the support role that the mana cost of his Q was dramatically increased. The mana nerf pushed him back out of the meta, where has remained largely invisible since.
However, his mana cost was reduced from 70 to 30/35/40/45/50 in 12.12 and his win rate in support increased from 47.2% to 51.7% in Platinum ranks and above. The second Q charge makes him incredibly powerful in lane, as he can engage from afar and land 2 Qs to form an effective CC chain. In team fights, Amumu main job is to find huge multi-man ults to lock down the enemy team.
Seraphine received a notable buff in 12.12: the slow/stun duration of her E was increased by 0.25 seconds to 1.25 seconds. Her E is on a pretty short cooldown and the stun can be procced using her passive or if another ally slows an enemy, so it's possible to get off a ton of stuns throughout a game. This buff has also made her ultimate even more threatening, if you can land the E as a follow up.
Given how versatile Seraphine is, she can be played as an AP carry in the mid/bot lane or as an enchanter support. Seraphine is an fantastic pick at the moment and sits at above a 51% win rate in all 3 roles. In the bot lane, her win rate is an incredible 54.4%% win rate in Platinum ranks and above.
While some of the most dominant ADC's like Senna, Zeri and Lucian have received nerfs over the last few patches, Miss Fortune has quietly become one of the strongest on the patches. She currently sits at a 51.3% win rate in Platinum ranks and above with the Arcane Comet/Lethaility build.
This is due to Miss Fortune's strength at multiple points in the game; she can deal a ton of poke damage in lane, before transitioning into an team fighting menace later on with her ult. She also synergises excellent with some of the best supports on the patch, such as Seraphine, Renata Glasc, and Ashe.