I've been trying to get into a group with the dungeon finder on 2 different toons now, when i reached level 15ish. Both are specced into healing, but I cannot seem to find a group and the DF doesn't give me an estimated time in queue. After a while, the DF just stopps working and disapears, and I cannot reactivate it unless i relog.
If you aren't level 80, you won't get people who queue in RDFs, because of the high rates. People tend to level up fast and can't be arsed to run through dungeons at low level as in their opinion, questing or grinding might seem like a faster idea.
However, you may use the dungeon finder with friends in your group; it does work as intended. You just need people to queue for it.