Walkthroughs of standard maps, focusing on SPEED.

Chingis, for "Raise Dead," earth magic is still useful for two reasons:
1) The skill level reduces the amount of mana required for the spell, and you can never have "too much" mana;
2) Advanced earth magic raises 30 more HP than the basic level, and expert level raises 130 more. This is not insignificant at the early levels of the game and hero development.
In general, necromancers are indeed luckier in this regard compared to living creatures: Raise Dead is a 3rd-level spell, while Resurrection is a 4th-level spell, so Raise Dead is learned earlier and has a higher chance of appearing than Resurrection, all other things being equal. Finally, if the Earth Magic skill is not advanced or absent, Resurrection only lasts until the end of the battle, meaning the dead will still be lost afterward.