The fun you ask? Where else do you meet people that go afk for like half the instance, people that try to push the tank like they where in the MDI and if he pulls more it's just wayyyy to much to handle.

damage dealer that stand in the fire cuz they need to DPS and cry after they die cuz the heal0r can't heal 5 people at the same time for 10 minutes.

The one guy that ask for just every item that drops even its an upgrade for your self and then is angry cuz you just don't want to give it to him. The classes with pets that pulls everything after you explain a shortcut to them and told them to please - for the love of Odin - put your pet away.

The min maxer that tells you how to play even its a low key like +3 or so. That also used to play 20+ keys everyday but that one toon is just a twink, so it's okay that you carry his ilvl 266 ass in the key.

The hunter that want to play a melee rexxar in beast mastery so he just can't use a ranged weapon, cuz c'mon dude - it's just a game, let me have my class fantasy even I deal less damage then a healer. You ask where's the fun? Well idk.