Don't forget enslave mind. ok it's astral 4, but with R'lyeh you can have it easly.
It's twice better enslaving an unit from killing it. And you can keep the enslaved ones after the battle
bladewind : it's a good spell only if your mage have a good precision.
Air spells: I hate friendly fire, so my air mages cast invocations : false horror, Phantasmal Warrior, gost wolves.