That's because there is a bystander theory when you get large groups of people together. They think they can simply do what they want and someone else will pick up the slack or do their job for them. This seems more apparent with DD since there are more of them, but this goes for everyone. My first run of CT2 last night took nearly the full 1:20 due to multiple wipes on each boss because people wouldn't listen.

Edit: But you have to consider that it is the first day also.. I consider myself a very good player and even I had my mistakes. Until more people learn the mechanics it's just how it will be. Gotta give it time. Even though my group struggled, once we wiped a few times and learned we did the fights very well and with minimal deaths.