I wonder how many of the new PC players have downloaded the demo and skipped the SP game? After some time in SP you should have a basic idea of how the different classes act together and the basic mechanics.
The proving grounds is too easy to miss, so they may not even has gone through it. I entered a game with three players standing by a rogue door with the rogue doing nothing. I didn't have a mic set up, and even if I had, by the look of some of the names I probably couldn't have communicated anyway. In the end I dragged them to the next level, and demonstrated as well as I could. They were fine in combat though and we cleared the dungeon. Hope they enjoyed it.
This has happened to me too. Bonus, it was one of those tiny rooms that spawn no enemies. I couldn't stop laughing, so my sister came to yell at me that I am crazy.
Some of the people probably just take a look at the classes and say "yeah, lets roll", and that's why you get legionnaires that don't generate guard and keepers that don't use barrier not even on themselves and spend half the game floor-faced.
On the bright side, there are also people like the archer I met on threatening recently, being quite helpful and not dying... unlike the level 19 reaver that previously wanted to kick him out of the lobby.In some cases it boils down to how much common sense one has to answer questions like " i am a keeper, should I charge those three enemies rambo-style and don't put barrier on myself, ever?"