Guild Wars 2 Combat Goals Explained

In a new developer diary penned by Guild Wars 2 designer Jon Peters, we learn why the game's combat system is not only being designed away from requiring a "holy trinity" of professions, but why it actually "won't allow it".
Another important part of Guild Wars 2 combat is mobility. We felt that in order to get the dynamic and visceral feel that we wanted combat to have, players needed to be more mobile. A lot of work went into this from animation systems to animations themselves allowing skills while moving. It takes a lot of pressure off of the skill system and puts in back into movement, tactical play, and ground control the areas where we wanted the game to be focused. Couple that with dodging arrows and double tap dodge rolling and you create a combat system that is more like a first person shooter where finding real cover, flanking and other more realistic fighting techniques find a lot more use. This again de-emphasizes the importance of roles and focuses players on what we intend, which is how their profession plays.

We've said this a few times in a few places but I can't reiterate it enough: We built this game so that they professions act as play styles, not as roles. Each profession can support, control, and do damage. We believe that this creates more dynamic combat and more distinct professions because there are more play styles than roles.

One of the best ways to explain this is with an analogy. In a first person shooter there can be a variety of weapons, from sniper rifles to rocket launchers to machine guns and shotguns. No one looks at these weapons and says, (They're all the same, they all just do DPS.) Why should an MMO be any different?