Tactics for playing as the Dwarves.

Here's a question about character development. Is it worthwhile for Dwarves to learn machine control skills? I've upgraded skillful machine control, ballista, the skill that grants rapid-fire ballista, rune machines that increase initiative, and fire arrows, which pierce unit defense. As a result, I created a powerful unit that can kill at least 50 units at a time. Is there anything else I can upgrade instead of these skills, considering I've already spent more than 5 skill points on them?