druid healers at lower levels

[Viorus]

You will NOT be passed over. Resto druid is more than capable of healing any dungeon. Yes Priests can rez more, but usually if somebody dies, the rest of the group follows. Don't let the tank die!

[Norjak]

Druids are capable of healing 5-mans at lower levels - just make sure you have gear with enough int+spirit & use ranks 3+4 healing touch (most mana efficient ones) so you dont constantly go OOM in the middle of every pull. Healing spec is "nice" but not mandatory, I was spec'd feral while leveling up & healing dungeons wasn't a problem. As has been already mentioned, make sure the tank is appreciative of your mana situation & plays accordingly...you can also make use of consumables at your level if you have them.