Ban kicked players from instance for the remainder of said instance.

[Niwashi]

you sure that ALL those that are kicked are trolls?

In the case of this proposed rule, it doesn't matter. Whether it's a troll being justifiably kicked, or a legitimate player being unjustifiably kicked, either way, they don't belong back in the group that just kicked them. The only difference is who is being protected by the rule. In one case, a group is protected from a troll rejoining them, and in the other case a player who was already unjustifiably harassed and kicked once is protected from being back in the same group to be harassed some more.