Accuracy for casting aimed spells is now determined by the appropriate magic school, with a bonus to any aimed spell (regardless of involved magic schools) from marksmanship. The Spell Aiming skill is now obsolete, and points in it will soon be migrated over to Marksmanship.
Multi-element spells will vary in accuracy depending on the elements involved. A spell involving 2 different elements would be 50% of element A plus 50% of element B mancy skills. 3 elements would be 33.3...% for each element involved.
Spell accuracy changes
Spell accuracy changes
The lore compels me!