I do instances as a tank. If they insist on running off without me while i watch my cutscenes (if it's the first time I do whether they like it or not) and they die then tough luck. Pay attention to where your people are.
My first CM run I told them straight away I was new and would be watching cs. Nobody commented on that so things were going fine till that one fight with the airship firing at the ground and everything went to hell. I didn't know where to go and my map was still partially blank and one person was like "Tanks! What are you doing? ZOMG WTFBBQ!". I just shook my head and ran around trying to find them. They had all died and were heading back when i found them and then it worked fine.
I also barely step over the purple line and wait there till I see everyone appear before attacking the bosses. This is how things should be done.
