[Xargon]

Some remarks about Sacrifice:
Maybe you have already tried using magic shield before sacrificing units - while it does halve the damage received, it also halves the health gained by the target unit, so it is not really useful. However, I recently noticed sacrifice does astral damage, and if you use the gift bag, there are items providing resistance to that kind of damage: the ghost armor (20%) and the chaos crown (a whopping 50%). This resistance lowers only the damage received which makes sacrifice pretty overpowered. You get 30% of the damage and 60% back if you have sacrifice lvl3. In my current mage game (having found both items), I can restock half my army from scratch in a single fight (I haven't lost any units since Verona, but it came in handy nonetheless as there were a meagre 6 demonologists to be found in Teana)...
edit: Of course, it is much more effective to have multiple "sacrificial" units and then resurrect them all at once with paladins than to alternately resurrect two stacks to build them up.

(The chaos crown is awesome anyway... 50% astral resistance is great against armageddon casters, and 50% magic resistance is great against a lot of other casters and some creatures as well... if you use only one black dragon or something similar, the gloves of the destroyer will be more valuable, of course)