Which class should I use for healer?

How about monk? Elementalist isnt a healer class. Monk is the most versatile class for heal/prot

Well. Hard question in my opinion. Ele with the proper setup can be quite a good prot<-healer. Monk as its speak for itself it is born for this kind of stuff. In other hand, i would try ritualist. I did play some ritualist healer/prot/dmg build combos and my opinion is kinda fun and maybe others can think it is bs, but it is effective. Everything depends what you wanna play, what team comp, heroes etc. But i would give the rit a shot.

I have no idea about PvP, but for casual PvE:

Monk has healing and protection.

Ritualist's spirits can fill a similar role, and ritualist has some direct heling skills.

N/Rt is a versatile healer that has lots of energy due to necromancer's primary attribute.

E/Mo can heal, but relies on boons to be kept up. (Ether Renewal)

Dervish with Avatar of Dwayna can heal.

I'd recommend N/Rt.

Been playing ritualist in RA with the Flux. Lots of fun

been playing ritualist healer in cooperative mission with people lately and it’s quite fun

Ele healer can outperform most others with SR+5 and high energy storage.

Get 12+1+3 energy storage, keep aura of restoration active and get Soul Reaping on a staff or wand.

You can run healing prayers or prot, there are a few elites you can use.
Generally you will have 100 energy and gain 5 back every death 3 times every 15 sec and gain 1 energy back per spell cast.

If you run Ether Renewal, you get 9 energy back per spell cast, and can just spam spirit bond on your entire team.