I want to say something about luck. It's really useless to take this skill in the late game, as luck can be increased with artifacts and buildings on the map. But on small maps, where all of this is scarce, it's worth taking luck. Soldier's luck is quite suitable for skeletons.

Added 2 minutes ago

I don't quite agree. With Vampire Lords, the effect of Soldier's Luck is still not allowed and it is unknown whether it affects the percentage of sleep or not. The only parameter that definitely affects it is the number of vampires in the stack.