My latest game experience
So I played mostly Aram within the last weeks but decided to try one game of normals in between. I actually had to look up what champs should be banned and based on that I banned Kai'Sa since our marksmen hovered a different champ anyway (and was last pick).
Now the enemy mid laner picked Leblance and despite our jungle Twitch to score first blood, he fed her pretty hard unless she snowballed and one-shot everyone else for the rest of the game. Despire me building a totally situational 
she basically one-shot me in 0.63 seconds and continued to do the same with other champions as well.
The enemy jungler stole baron, took all drakes plus elder dragon, they took all our inhibitors down while we only had taken like 3 of their turrets. 45 Minutes into the game we somehow got to snowball the enemies one after another and pushed through their base thanks to our unlucky Twitch jungler assassinating the super fed Leblanc (19/11/6) several times before that. We won the game and I really don't know how that was possible to turn around. We had a pretty neutral team attitude (Twitch asked for a surrender but didn't ask for another when we declined that). Nobody flamed and some gj were found here and there on top of that.
Yet - and that's the whole reason of the thread - the game was #not fun It felt so incredibly horrible to be oneshot by leblanc constantly even though building against her, exhausting her, flashing away from her follow-up E but that didn't matter at all. When leblanc decided to kill someone - that one died. At this point I want to add that the LB player did play very well. He deserved his score and he deserved to win, but for me that champion ruined any fun on the game. So yeah, good job on that Riot. I don't call you failing to balance the game, but if your goal is that players have fun playing it then yes, you failed at delivering a fun experience to me due to leblanc.
and the penetration runes. That's how mages and ap assassins are supposed to deal damage. What's the point now? You were apparently a squishy support, means, you were the easiest victim with a naturally low level against a snowballed champion. Any assassin could do the same. Your team didn't have any tank. Your job was it to keep the assassins away.
And your team had some of the most Toxic champions of the roster, including Twitch, which is not any better.
The problem is that there will always be a couple champions who can be toxic. But they're fun to play and not necessarily too strong. Get over it and ensure to have a good peel and a good coordination next time. That's even possible when playing with randoms.