Sorry, wasn't sure where else to put this - it seems like it is not an intended mechanic but I wouldn't quite call it a "bug".
For the first time this evening I tried to form my own raid to finish W4 and had the raid almost full, when a new person (Name: What Are Boons) suddenly joined and kicked me and half the other members. I assume him and a couple of other people who had joined decided they would just steal the raid instance.
I doubt the ability for someone to steal your raid instance is intended, and it seems unfair players should be able to skip raid bosses just by joining your squad and kicking you.
Perhaps Anet should make it so if you kick the instance opener, everyone gets removed from the raid instance?