WowAce

When the window is popping up at the start of a 5men dungeon, that could be cool to know if someone (in that group) never finished it.
People are really reluctants to say that they need explanation on how some bosses need to be played, so that could help to figure who needs help

(no i dont think about Oculus... or maybe yes.. ;) )

Was thinking about this, I'm not going to rule it out but it's a bit of a pain to implement currently.

I would like to see this... but not really for dungeons but for the raid /eg summary.

This is typically one of those things that's going to give wrong impression. Having a few 80 characters of all roles myself, I've done all dungeons and raids, just not on all my characters. It's nice to be able to see what a certain character has done, but it doesn't say anything about what the person playing it knows and has done. I've just lead a successful onyxia and ulduar FL weekly raid, while not having the achievements on the char I was playing, because he just dinged 3 days ago.

Not to Disagree with yiNXs, but it would help to know which person in the group may or may not have completed a raid and then to ask them if they have or have not encountered the bosses. I would rather have someone tell me they have completed the raid on a Main and they know the fights then to get halfway through the dungeon and wipe cause we assumed they had a main and knew the fights.