Scripting Spell priority

[Monkeylimits 0]

So 2 things happen that I notice I dislike.

A) When my Hp is low, my shaman will cast Healing Wave.....which is what i want it to do.....but hell cast once when he goes below the hp set and then after he heals and is at about 75-80%, hell cast Healing wave again.....I only want him to cast it once.....I tried turning on the "ONCE PER COMBAT" option on the skill but sometimes when i have multiple mobs on me, hell cast it once and then when it comes time to do it again he wont cuz it told him once per fight......so how do I get it around that?

B) When my mana is low low low and im burnt, and my hp is getting low, its near end of a triple mob fight or something.......all abilities are greyed out etc but hp is dropping. rather than him waiting for Healing Wave to be reaedy, how do I make it so he cast lesser healing wave instead?