Please Stop Complaining about an Assassins ability to kill you
Seriously please. everywhere I see it. "hurr durr zed does 50% of my life if he hits me with his combo".
No shit. He's an assassin who literally is specifically designed to kill you, be slippery/safe, and do it very very quickly.
Assassins can be a balance issue if they are wildly over tuned or they aren't easy to kill when they make a mistake.
Everyone will always have a circle jerk about whatever is currently the meta/too strong. It changes but whatever comes up its "this class is too strong". Tank Junglers are op and then all of sudden early game junglers come back and you don't see people whining about them anymore.
The reason is it feels bad to get fucked up with what is PERCIEVED as so little of effort. You see the Kha'Zix running at you and you know you really can't fight back since all he's gotta do is Q you, stealth, and Q again and u are deleted. Hell if he's fed enough he won't even need that 2nd Q. What makes it more frustrating for people is not only was it seemingly easy for him to erase you from the map, but he's jumpin away and havin a good time being safe and free in his own jungle right after. Your team was nearby but he's safe as fuck. That can FEEL infuriating. But its part of the game. And its balanced because that Assassin had to come in on you at the right time or you had to be alone.
If an assassin can't kill someone they literally don't do anything else and are useless. So of COURSE they are going to be good at killing things. Think of Kat or Zed or Kha. What do they bring to a team if they can't kill a caught out target? Two of them bring a moderate slow and one brings nothing but damage before being blown up. So please stop whining about they are so annoying or broken or too strong. They are meant to be able to efficiently kill you, and they should do it better than any other class in the game since that is all they offer. And yes they should be safe and mobile. That's the whole point. Assassins will also always be snowball masters.
Learn to play around them, don't get caught out alone, don't get mad when you can't outplay one and they erase you with ease. Stop QQing when they crush you early game and run rampant on the map and please for the love of god build a defensive item if you feel its your only counterplay. (i.e. you are standing in your own team and still dying to an assassin)