Description
Proficiency in visualization is important for spell casters as it reduces the need for somatic components (hand and arm movements) in some spells, allowing the caster to imagine performing the required actions versus actually performing them.
Even with visualization, however, somatic components cannot be entirely replaced, and thus the power of the spell will most likely be reduced if it is cast with the actions visualized. Some spells (those requiring 80% SCC and above) require too much power to be cast in this manner at all.
It is difficult to maintain the proper mindset required while casting a spell and visualizing its required actions, therefore the effectiveness of visualization is cut in half during combat situations.
Visualization is useful when a caster's hands and arms are restrained through spells such as web or imagined (such as through mesmerize).