Ban then everyone who is worse then him. I told you once that on top of castle is healing tent we used. One is destroyed,so someone built it on top of castle and that tent survived and i used it to heal.
The problem is not the overall k/d, the problem is when someone waste tickets.
I'll give an example that you can understand :
Hearst : k/d 77 15
Then he joins a castle defence (less people shooting, no need to climb ladders, etc...)
Hearst : k/d 20/25
He suicides a dozens of time, gets bored, decide to fight, jump down the walls, loosing 1/2 of his initial health, but still manages to get kills, since he's so good.
Now, Hearst has stricly nothing to do with nogu, he's just an example of how you can't rely only on k/d at the end of a battle.
It's nogu's attitude that is bannable.