btw, the trinity exist in gw2 as well, and on the higher end content you need a guardian(tank specced) and one healing focused player, unless you plan on using ages to finish the content.
Remember how much some friends of mine was suprised when i joined them in a dungeon with my guard and all the sudden everything they had struggeled with before just melted because i could soak up all the damage and they were free to focus on dps.