Wait are you not micromanaging everyone as the only time I have had an issue with field is if i was not paying heed to the field. Also npc companions class can be changed when you recruit at joy or if you have 4 mates get them to join you. get them to make your compans as you like then save and have them drop.

As for what spells do is it not mentioned in the info panel also there is a circle that shows the area effected by the spell (only problem is water made by rain as that is a big ass circle but stays near pointer.).

Rain is a must if fire or poison is your foe also hail is good at getting rid of poison.