You didn't Nerf Kaisa hard enough.

Teammate 1 : "hey guyse we went full retard" Teammate 2 : "let's blame it on the champion" Teammate 3 : "even better let's make a post about it on the boards" Teammate 4 : "but we were all going 1v1 vs the fed kai sa..." All the other teammate : "shut up bronze 5"

be honest that's probably what you did i think

Reminder than a marksman should never have this commented towards him : "He's too tanky"

these items should either be melee only or gutted to oblivion.

So, you were vastly winning at 25 mins, and in 7 mins Kaisa managed to get 31 kills and deal almost double the damage of the second guy in game? Seems legit. Classic Silver 3 crying post.

You lost Baron (probably stolen). Then at a fight at dragon, you all died, probably because you botched the fight hard and then with Baron and 4 people dead, you lost 2 inhibs. Nothing really weird. With the kills that Kaisa got, she was able to carry. Kaisa already had 16 kills before the dragon fight, and probably around 200 cs, which means she was close to a full build. Destroying you in a fight doesn't seem strange. You just ignored her and she destroyed you, just like any other super fed carry would.

All I have to do is look at her kill timeline to see she has around 5 kills by 7 minutes in. and by 20 minutes in she already had around 17. The only person to blame for your loss is your own for not conforming to a standard team comp.

You had no tank or team fight potential and it's because you all wanted to play whatever instead of just taking one for the team.