Ok, I'm just gonna get right into it. I'm sure it has something to do with skill and all, but since the Kass buffs in patch 7.7 I've found it increasingly difficult to win lane as almost any mage and literally impossible to win lane against him with champs like kat and riven (varies on the player I guess). The fact that kass can just build roa and never die against kat 1v1 is kind of messed up imo. Into riven or any mid lane ad he can rush tabi while building roa (which probs is also op since it's a 1100 buy that counters 1 shots better than maw into most mage assassins).
Kassadin is supposed to have a weak laning phase considering he is unkillable if he isn't careless past 6 right? I don't understand why he is able to win trades through full combos of kat or riven. ESPECIALLY RIVEN. She can cancel his w and still lose a trade through his q-e. He has these cooldowns on like 5s while riven in lane has average cds of about 10s with 10% cdr runes + 5% masteries. Kassasin is and I'm assuming is still supposed to be an anti-mage champ, so why is it that he can legit 1v1 riven at level 6.
Now just consider every single champ in the game and which ones are the most obnoxious when fed. Which ones have a way to play against them when fed. Now think about kassadin. If he gets a few kills in lane it's basically gg bot or top. He runs tp and has insane map presence or can choose to dive mid lane every time they run into lane with nearly 0 risk. Mid lane opponent can't farm, therefore can't buy items, leading to rage often at jg or just tilts overall.
Did I mention that it's almost impossible to lose trades against mages in lane? Q gives a magic shield and every spell cast you do gives him his e which had it's cd reduced in patch 7.7 (also increased ult scaling). His ult through a few cdr items gives him flash every 1 second by late game which idk, sounds a little broken. He can start whatever the hell he wants and still rarely dies. He lives on a sliver of health after your ignite level 3? No worries just b and tp back into lane. Now mid lane has no ignite until level 6. Free lane free game, RIP bot lane.
P.S. I'm not one to check win rates and ban rates champs, so if nerfs or personal opinions go based on statistics, then this chunk of text is basically worthless.
Probably biased af but those are my main thoughts on kass.
Few other champs I think should be looked at (in terms of balancing) are: Vlad, Fizz, Lulu, Mao, Talon.
For those who read to the end, have a great day! coz i have exams in a week. :)