THE HOLY TRINITY: In Guild Wars 2 any profession can do anything it wants. Everyone has their own heal and everyone is expected to do what they want to do. Every profession is self sufficient, and success in combat depends on strategy, movement, and good teamwork.
Sorry, I'm a little confused as I'm new to the game. I can see that everyone on the team has to be on the same page in reference to positioning, movement and target order, but what else do you mean when you say teamwork, especially if everyone is doing their own thing? Are you referring to combos?