It's a bit iffy, really. In the Hall of the Novice, the tank NPC claims to "keep them occupied" while you do your job, so it's probably the closest you'll get. Lorewise, you wouldn't be able to just run past (or THROUGH) an armed person to kill someone else without finding a weapon inside your neck on the way. No real excuse for ranged enemies, tho.

Otherwise, yeah - gameplay/story segregation. Many of the fights you lorewise do alone, you actually do with 7 other players.