Slow Missiles is a pretty funny spell. It allows you to run circles around enemy missile weapons and spells. This is also very useful against Multiple Shot Unique Monsters that are difficult to avoid. Slow Missiles will also make it easier for other party members to avoid enemy missiles.
Use Slow Missiles against those pesky Abyss Knights and Oblivion Knights. If you see fire coming from them, run up ahead and cast Slow Missiles then retreat. This is very effective and can allow you to easily dodge their deadly fire.
Through strict martial discipline and focus, an Amazon warrior can attune herself to her environment and the dangers around her, allowing her to react to these hazards with superhuman agility. One aspect of this ability is her knack for avoiding missile fire. Just as the Amazon must master the bow and javelin, she must also learn to defend herself from these same weapons. When an Amazon uses this ability, incoming projectiles appear to move slower than normal, enabling her to avoid them.
↑Diablo II Manual, page 58. Blizzard Entertainment, 2000.