people do stupid things like playing tanks without shield :X
Had a Full Rakata DPS in dps spec, in tank stance, with no shield generator trying to tank LI HM... Same tank I got in EV SM 10 minutes before and they got 2 shotted by the lava/stompy guy whose name evades me at this moment. We couldn't do any bosses with them at all. It was completely awful...
Now on topic: You have to teach people, the people doing it without friends are generally people who have never done it before. I usually give people 2-3 attempts to improve, if they don't I kick them. After fully explaining what they need to do or watch out for of course.