There are many ways to make a healing monster. Maybe arm them with heals, maybe scrolls, maybe abilities. Mostly, it is best they stay back, but of course, healing allies and themselves is the point.
Concentration is the key - as otherwise them healing spells will go down the drain. Also, there is a rank associated with each spell, and only critical and serious cure wounds will ever be cast all the time - so don't expect cure minor wounds to be used by a dragon.
Also note that an NPC will use healing kits, and thier feats, on themselves. They will attempt to use negative spells on themselves if they are undead, and potions if appropriate.
I will, eventually, improve what target to choose, but at least GetFactionMostDamagedMember works. It will check better for nearer targets at moderate damage, and only move futher for higher damage. Out of combat, they will move to seen people in 40M, to heal them as much as possible with spells that they might not normally cast.
Some ideas for these supporting spellcasters are:
And I cannot really think of much variety on this, but there are countless ways to impliment the above. I would never rely upon harm though, as it can miss, but implosion, destruction, and storm of vengance are all good (mind out for friendly fire for some though!)