I think death spells such as sacrifice, empower, and dark pact are unfairly designed to help other schools more than the death school since death has higher damage to their own school. To fix this the spells should do moon damage instead of death damage.
I think that damage is what helps balance those spells. I am a death wizard, and I've found that those spells are often super worth the damage because they can turn you into a powerful support.
However, with spell-writing it would be fun to see it possible to upgrade those spells who they either help more (blade does more damage or something) or deal less damage. Alternatively, it would be interesting to see a high-level Sun-School enchantment for sacrifice spells only available to Death wizard that lets you alter the damage type to another school.