Riot, I don't think your game has correct limitations for assassins.
As odd as that sounds, I find that there are some types of champions where Riot just struggles, yet they pursue their production anyway. Assassins have been a pain in their arse for a long, long time now (Well, with how they've handled it we're more bothered with it than they are) and no matter what they do they seem to weasel their incredible bursty selves back onto the scene. When sometimes it's more how the game is designed that gets them back into the meta. I think it's fair to say assassins in League have minimal counterplay, champions like silence LeBlanc, pre-gutting Kassadin, old Akali, DFG mid Evelynn, Kha'Zix, what those lot have in common? They've all been nerfed, pretty heavily, sometimes warrented (LeBlanc) sometimes controversy has followed (Evelynn).
But what I find is that balancing acts in this game seem impossible to maintain, due to the nature of the game assassins and bursty characters are hard to keep in line comparatively. Tons of damage on wheels is something that I don't think league is ready to handle. Other games have certain mechanics in place that keep those types of characters in line, while Riot seems to be lacking.
Dota generally has really high mana costs on their damage oriented characters, meaning that they have to be very choosey with their spells a lot of the time and it limits their early kill potential unless they play it correctly. A lot of assassins truly have a weak early game that gives their opposition time to form, perhaps shut them down or get them behind, and itemize against them. Not to mention, their spells don't scale meaning that their effectiveness eventually falls off or they go right clicker. Mobility is a rarity and right clicking has plenty of counterability.
A lot of Smite's assassin are just plain hard to play with particularly different skillshots and the very nature of the game where everything is a skill shot and dodging is a major part of the game. To be able to pull these characters off and snowball to big proportions requires either skill, poor plays on the enemies part, a certain degree of luck, or some combination of the three.
Meanwhile with League, the system seems to work in their favor a majority of the time. With plenty of mobility and and safety in the early game completely shutting them out of the game is extremely difficult and does not work all the time. Itemization prevents you from getting absolutely destroyed, but squishier characters need damage to do damage, if they build no ap/ad than they are going to be of little use. Nothing feels quite as lackluster as a second item 
Mana management has fallen out of Riot's flavor and perhaps wrongfully so, once upon a time damage dealers had meaningful mana costs that gated them to some extent, yet all of Riot's incredibly powerful assassins seem to lack either meaningful mana costs or mana as a whole.
tl;dr Riot's assassins lack limiting factors that other games have in place to keep them in line in a style that already seems to suit them, leading to them always being a pain in the arse.
Thoughts? Comments? Concerns?
is the most balanced assassin in the game. He has a semi-weak early game, that if he doesn't snowball, he's not very useful. He generally doesn't have an escape, (as he has to use ult for extra damage, or to speed himself up to get in range to E), and he's very squishy.
), In all honesty, I think Riot needs to make mobility MUCH more expensive.
If you're going to complain about a set of champions that aren't Morde/Skarner/Darius right now, I think you're looking in the wrong places.