I have tried for an hour to become part of a group to do "The Banished Cells". The random grouping is a disaster!
Groups almost never contains healers or tanks, with the result that group members always decide to leave the group, and you have to start searching for a new group.
After joining 50 groups finally I found a group with a healer! It took 30 minutes to finally get a group like that. We entered the dungeon... And we were not able to see each other, we were not in the same phase. So everybody left that group too.
During the beta I did some group dungeons, but I have not been able to do dungeons at all after release.