Duty finder = deal with what you get, sorry sometimes you get that one dps doing less then the tank, but DF is luck of the draw
Party finder/pre made = parse and kick all you want(provided you are the Party leader) or if you aren't and someone is underperforming and won't take your advice(like say a ninja refusing to use a poison in a RavEx farm) leave. If people blame you for that oh well standards are different.