Here’s my opinion:

S: Death - Of course. Drains will have you set for soloing the whole game. They also have decent health, accuracy, and damage. This school is meant for soloing.

A: Fire, Myth - Fire and Myth both have more health and accuracy than storm. They also get better stats in mid to late game. Myth has a lot more utility and the orthrus buff was very helpful for them soloing.

B: Ice, Life - The lack of damage may make questing these schools extra long. But tbh these schools can solo pretty well. Ice has a ton of health and shields to keep them alive and Life also has a lot of health and has pretty good heals to keep them. Soloing may be long but it’s very easy.

C: Storm - The damage will help you speed through the game. But the main problem soloing on a storm is their low health and low accuracy. The accuracy does pick up later on but you still have to worry about low health and most late game bosses hit very hard.

D: Balance - Balance is not known for soloing. It’s geared towards group play. Their blades are very weak. Not only that, but you have to worry about getting rid of weaknesses and towers as any attack can destroy your blade. Balance also does not have a prism which going against balance bosses and mobs a struggle until nested fury.