I started playing during the x12, so the first instance (in this game) I could get was just after 3.0 came.
I queue and get KDY: Me, 24 sorc, 2 30ish sorcs and a 47 sorc. I enter, type 'First time here, first instance ever so tell me if I need to do anything'.
While I was typing, people scatter and start attacking mobs all over. Oh well, I follow the 47 and attack his targets.
This works till we get to the 'defend the dock' part (not sure about the name). After killing mobs that came, 2 people run off to the left stairs up, 47 goes to the right ones. I follow the 47 up. We kill some mobs on the stairs and then he pulls the group on top, in the middle. I look and see other 2 sorcs dead and 2 elites (champions?) in the group he pulled.
I focus on one I can see from the stairs, bring him to about 10% when suddenly other mobs start attacking me. I run down, killing the elite on the way and los/kite the rest of the group around till I got help: a PT and operative. Confused to hell out of me till I checked chat log later: group changed 6 people while we were running as people died they would just leave.
Finished it without problems after that, but still it's most confusing instance I did in a long time. Next time I go I will have to ask for tictacs again, cause I have no idea what was going on.
Another fun part: When purple item dropped, I would check what it is and get 'Just press greed already ffs'. I look better and see a) it's a rep item and b) everybody else needed. Right, I'll greed.