My typical LDoN groups have a druid for the healing and the pally for back up. A guild mate who's dual-boxing. Anywho, no matter the composition, when the three of us group, we can add anyone else and always win. When just join a random group, the odds are against us as there are several newb 50-60 folks out there, if ya know what I mean. Plus I have run into several ego issues and just plain dumb newb mistakes (i.e. waking every mezzed creature in the room). I've had a wipe or two with friends, but we always win on normal or hard missions. Although Hard Rescues can be a bugger. It's great to throw someone into the mix and see what they do. The folks who can adjust their skills, as us bards do, tend to be the one's ending up on my friends list.
The best LDoN I experienced was a Ranger who decided to go on autofollow then afk without telling anyone. So we were less one tank, who obviously didn't aggro or snare anything and still won.
The worst LDoN I experienced was a pick up group of one egotistical bastage SK, a rogue who woke all MoBs I mezzed, a cleric who disbanded after a partial wipe, but before any rezzing, a decent druid and myself the night after lull nerfage. Well I died twice on overpulls and didn't have time to get CC on the first one and got overun by awakened MoBs on the second one. They blamed me for the cc issues, which may have been valid had I not look back on my logs to see "a blahdyblah has been awakened by the dumb-arse rogue" "Wiladancer is gettin his arse handed to him by a blahdyblah" So after getting a lecture by the SK who has a chanter on how bad I was at cc, I decided it was time to log.
Stick with those you know if at all possible. Just my 2cp worth.
Wila the newb