TBH this is a terrible idea, forcing the person already in a group to deal with a popup simply to ignore it .. the scope for griefing is huge and the benefit to that person would be .. what, exactly?
How many times do you think you'll be inviting someone who WANTS to be in a group with you who is already in a group with someone else?
Instead of the person not receiving a request and the sending receiving a "party is a in group". The person should be sent an option to join. Makes it a pain the the butt in Cyradiil when you have to send invites out to people standing around waiting for raid. Or perhaps I am going about this wrong? Thank you.