There will be some slight changes in the mid lane with all the new modifications announced for the next patch. Things like champion win rates, new changes, item build paths, the current meta, and many more were all taken into consideration while making this list.
Riot Games' lead gameplay designer, Mark Yetter has released the intended adjustments for the next week's patch 10.7. It seems like there won't be some significant changes to the mid lane, so after classifying the top lane picks , we have now prepared a list of the best champions you should find the most success with in the mid lane.
Diana - S tier
Diana has seen some nerfs a couple of patches ago which didn't have a huge impact on her mid lane kingdom. She has very strong snowball potential but even if you find yourself behind, it's not hard to come back into the game. At the moment, Diana is topping the win percentage charts through pretty much all of the ranks and since the patch had no big changes related to the mid lane, she will most likely stay on the very top.
Fizz - S tier
Much like Diana, Fizz has been dominating the mid lane meta for quite some time now. Once you hit level six, there aren't many champions that can survive your 1v1 all-ins. The ability to quickly go in and out in fights makes him one of the best team fight assassins. His item dependency is compensated with high mobility and easy escape mechanics.
Sylas - A tier
Sylas has a very specific playstyle that can surprise enemies in a lot of different ways. With the recent buffs, you should always try to max your Kingslayer (W) first as it provides incredible healing especially in elongated team fights which he thrives on. The unique ability to steal your opponents' ultimate and use it up against them in addition to being able to go on three different lanes makes him one of the best flex and counter picks in the game.
Ekko - A tier
Ekko is yet another high mobility AP assassin on the list. He has always been a strong pick in solo queue due to his aggressive playstyle potential and ability to easily snowball the game. A great combination of strong burst and CC on top with a get out of jail free card ultimate makes him one of the best mid lane champions you can climb the ranks with.
Neeko - A tier
Since her buffs in the 10.5 patch, Neeko has been doing pretty well in the mid lane. Once she hits her item spikes around the 25-minute mark, she really becomes a force to be reckoned with. She currently holds a 52 per cent win rate and since there don't seem to be any nerfs heading her way, you should definitely try picking her up.
Kassadin - A tier
Kassadin is the Jax of the mid lane. You have to play a really passive early game in most of the match-ups but once you get your ult, the roaming can begin. He has one of the strongest late-game carry potentials with a staggering 59 per cent win rate at 30 minutes. If it wasn't for his weak laning phase, where he can potentially get exposed and shut down, he would most certainly make the S-tier on this list.
Annie - B tier
Annie might not be the flashiest champion out there, but the impact she can have on a game undeniable. Her kit is pretty straightforward and easy to use once you play a game or two. Even though she's considered a champion for the lower ranks, she currently holds a 52 per cent win rate in Platinum and above. Pretty high for a noob champion, isn't it? If you play mid lane as a secondary role or if you get auto-filled, Annie is surely the right pick for you.
Azir - B tier
Azir is the epitome of the scaling champions, but unlike most scalers, he provides a pretty safe laning phase with incredible poke. His biggest downside is that he is pretty hard to play, especially for the lower elo players, but once you get the hang of it, you've got yourself a ticket for the higher rank.
Cassiopeia - B tier
Similar to Azir, she is also one of the best late-game powerhouses. Tank or squishy, Cassio doesn't care as her consistent damage shreds through everyone's health bar. A very stacked kit allows her to take over games, as the ultimate together with Miasma (W) can solo win a big number of team fights if used properly. Not to mention the ADC-like damage output she can produce thanks to her spammable Twin Fang (E).
Talon - B tier
It seems like Talon will receive some nerfs in 10.7 which demotes him to the B tier on this list. As a Talon player, you should probably try to find your advantages in the side lanes or in the jungle, since his mobility and roaming potential cannot be matched by any other mid laner out there. We’re not taking anything away from his laning phase by saying this - it's just that the way he can assist his jungler or cover the map in general, exceeds most other champions.