Skills for an Inferno hero.

Runes are decisive. And Helmar can help with the undead and vampires. I don't take Princes because they lack the "enemy has no resistance" ability. It's very helpful. Dwarves have low attack power; they'll weaken the undead, but won't break through the thick armor, so use runes, the Rune of Ecrocima, and a Warden Mage to help. I rarely use Subjugation; I think Berserk is better because it multiplies damage. So... if you have absolute defense and readiness, defend, don't attack, use runes, and everything will be fine.

Runes have the property of draining resources, and they are used only once. An upgraded rune is not an option until you have enough gems, and you will almost always have few gems. The Necromancer won't wait; he'll attack when there's a full resource crisis (usually in the middle of the game, i.e., the peak of Necropolis's power).
You're wrong not to take Princes; their Blindness is no worse than "enemy has no resistance." If it works, the affected unit can be out of the fight for a long time.
The fact that Dwarves have low attack power is a huge disadvantage that the Necromancer will definitely exploit. Mass weakening, vulnerability, and slowing will cause the Dwarves to lose control of the situation if they don't have Light magic. Even if they have Light, you can safely cast Subjugation on, for example, Thanatos.