It has little self motivation, so its AI dictates that it will do exactly what it is tasked to do.
It will not take the initiative and attack nearby enemies, only those it is tasked to attack or if it is attacked itself.
Weapons that are not 'blunt' will do half damage against skeletons (fire, arrows, etc.).
A horde of skeletons led by a skeleton lord will be a very effective combination - driven into a maddening frenzy of whirling sabres in close combat.
defeating a skeleton