It isn't worth the mana to heal a ranger. Its more efficient to just rez them.

If you like the idea of charming, but still want versatile classes, try Enchanter and Ranger.

This duo can work well a few ways:

Safer way
Enchanter pulls, is hit once to have his pet attack. Ranger snares to draw agro away from Enchanter. Enchanter fears, pet and Ranger beat on the mob.

I did this often on Live way back around velious era and it worked great. With enchanter haste and breeze, the Ranger can do great damage and keep the two of them healed here and there.

Dangerous Way
Same idea as above, but using charm instead of the mindless chanter pet. Ranger snares the pet each time charm breaks to give the chanter time to re-charm. Make sure its a blue pet so it doesn't out damage the two of you.

This duo is also great for any questing with track!

If I'm tanking for a group with a Cleric and a Shaman I'll have over 2500 health. CH is more efficient than Shaman heals and it's not close.