Which faction poses the greatest challenge for the Dwarves?

The Necromancer's development is too rigid; dedicating a valuable skill slot to logistics seems inefficient – at the expense of what? Here's the breakdown: defense, darkness, summoning, education, and spellcasting. What should be removed, in your opinion?

To Ereb: Subjugation is very effective against Gnomes, as we will have a complete set of runes.