It's easy every time i wanted to kill the world boss i did..
Always will be some gankers around and some peoples who want to do the event.
If you guys really want to kill it then you put away that you want to kill the other guild, invite them to the raid then kill everyone who doesn't want to join.. that's all
It's not just for world boss, inv everyone who can help you to reach your goal if he decline your inv then kill him...