Usually right at the beginning of the game I will design a unit with the +3 HP trait, the +3 defense trait, and the +2 initiative trait with leather, a shield, and either hammer or spears (if using defensive).
Sounds like a good strategy to me. I would probably choose something like +3 defense initially when my troops have almost no armour, and probably +2 initiative and Underdog (+3 attack vs. troops of higher level). Underdog is an excellent value early game damage enhancer when you're playing on higher difficulty levels and everything is higher level than your troops. If your troops have attack six then you're increasing their attack by 50%. Later on in the game Bloodthirsty is better (+50% vs. damaged troops), as you probably have attack 15+ and your troops get to higher levels, but it costs twice as much as Underdog, and Underdog gives a bigger bonus in a lot of cases at the start.
+3 hitpoints is cheaper than +3 Defense, and increases level 1 hitpoints for most races by 3/8, which increases their survivability quite a lot, so is certainly a viable option. Personally I prefer having Ironskin and one damage increasing trait. When I get leather armour I might choose hitpoints rather than defense. When you get mail armour you need to use a trait for that, of course.
