When you are first starting heroics, its a lot easier with a dedicated healer.
It is never required.
As you gear up some, most of us move towards 4x Elemental all the time.
I've got one shaman who is dual spec Elemental/Resto.

As far as leveling goes, mix it up.
Quest some, instance some and pvp some.
Take breaks whenever it starts to feel slow.
If you have another team you can play for an evening or three, that can help.
For a lot of the collections, everyone can loot, so be sure to assist the leader and interact with the corpse on everyone.

I would go Shaman x5, until the catch up to the Paladins level.
Then level Shaman x4 + Paladin.
And put the pally in the group at any level, if you feel like instancing.