That's the big picture, but what about smaller groups? In an interview with The Electric Playground, Lead Content Designer Joel Bylos explains the general idea behind the group dynamics:
We really feel that an MMO is a shared experience, right? It's very important that people work together to solve these problems. That's the greatest sort of feeling of achievement: when you work together with other people to overcome something.He goes on to say that it may be possible for players with similar builds to actually be viable even when they're grouped together. He specifically mentioned a group of all tanks' being able to tackle a dungeon if they all had a self heal. But how many players are actually in groups? Bylos says five, and raid groups are 10. No more worrying about finding those other 30 people you would need for those 40-man dungeons, thank goodness!