I hit the same brick wall in RFC (although i didn't try at level 11).
At first it sounds easy to control the different characters which basically comes down to healing the void and dpssing BUT actually doing it is something you have to get used to.

My advice is to get used to that playstyle by taking new abilities one by one.
Create a simple cast sequence for your dpssers (see macro thread) that assists the healer and nukes the target down till it's dead and actively play your healer. With that one macro alone you can do most stuff and add more utility when you feel the need. Don't try to do everything at once!

Second advice is to accept the fact that you will wipe and that you will wipe more often than with a group where 5 people can pull some stunts when a pull goes wrong.

Third advice is: Don't try to tackle the dungeos when you are too low. First it's frustrating when you go down, second downtime means slower progression. Personally I did SM still with lvl 44. The mobs were all green but I didn't die and could kill them so fast that the exp was good.

Fourth: Don't get frustrated. Leveling up 5 chars is tougher than leveling up one char.

Hope this helps,
Bunny