Developing a Necromancer hero.

2 Silovik Leadership on medium-sized maps is a gamble; you spend five levels and don't get any bonuses to your army, but you might be able to recruit someone (a unit and a half)…. It seems a bit absurd.
If you reach level 30 without Education, you lose thirty points to your main stats, which is twice as much as just reaching level 30.
Magic. Most spells are already cast with a 50% initiative discount from Dark and Summoning. As for the rest... well, I don't know; there are more useful skills.
And about Shriek, I already wrote that taking it when there will be battles on low levels (10-) is useless; there are more useful things. And when the levels are higher, other spells (various mass curses, slow, etc.) are already more useful.