While League of Legends Patch 10.21 mostly contains jungle champ changes, those changes do in some way affect mid laners. There have also been several champs who have seen an influx on their win rates mid-patch.
Here is the League of Legends Patch 10.21 mid lane tier list.
League of Legends Patch 10.21 Mid Lane Tier List
S Tier: Yone, Fizz, Zed, Katarina
Fizz is a great champ to add to your mid lane rotation simply due to the amount of impact he has in game. The aquatic yordle can deal out immense amounts of damage and is mobile. This mobility helps in escaping but also has allowed Fizz more freedom to dive towers more often. That makes Fizz a devastating mid laner that remains a threat throughout all phases of the game.
A Tier: Annie, Yasuo, Nocture, Kassadin
Although Annie has the tenth highest win rate according to op.gg, her kit is extremely user friendly and similar to Fizz, remains a threat throughout the whole game. Players are often deterred by her simplicity and what seems to be a "weak" ultimate ability, but this is what makes her strong. Especially at low elo, she can tear apart mid laners who have bad macro and fall behind during the laning phase.
B Tier: Vladimir, Ekko, Talon, Galio
Trundle and Lee Sin will receive buffs in the upcoming patch. But what does that have to do with Talon? He isn't the top of the B Tier nor does he have a particularly high win rate. One of Talon's key characteristics is his mobility and with champs like Trundle, Lee Sin and other champs reliant on running enemies down or landing skill shots, mobility is key. Avoiding abilities and then counter-attacking is what makes Talon so strong if fed, so make sure to keep an eye out for Talon.