Fireball discussions always make me laugh. In a campaign I'm playing in that's 15th level, I have a bladesinger Wizard. I didn't have fireball until the party chipped in and bought me a scroll because it "wasn't right." I've never cast it.
Now in the game I'm currently playing, we just hit 11th level and one player has an evoker. People ask why he doesn't seem as powerful as the wizard in the other game, and it's because he casts pretty much AOE damage spells only. I bought him a Counterspell scroll and said "please memorize this so that my bard doesn't have to take it to keep us alive."
The Wizard really is a class that can range from god mode to "okay."
Every DM cries tears of joy when a "mage" player decides to play a "blaster".
it's just damage. and not that good of a damage source.
Fireball might be OK at 5th level, but the scaling is horrible.
how to make fireball better?
scaling:
4th level, 10d6, 25ft radius
5th level, 12d6, 30ft radius
6th level, 15d6, 35ft radius
7th level, 17d6, 40ft radius
8th level, 19d6, 45ft radius
9th level, 22d6, 50ft radius
another option:
reducing radius to increase damage.
every 5ft reduction in radius increases damage by +1d6
reducing radius to 0, makes fireball a ray with a ranged magic attack.
that would make 3rd level fireball 12d6 ray of fire with ranged magic attack.
and 9th level fireball a 32d6 ray of fire(still less damage than Meteor Swarm).
another option #2:
throw out scorching ray.
reduce fireball level to 2nd level spell:
5d6 fire damage, 15ft radius, dex save for half
with reduction in radius and increase in damage it would be:
6d6, 10ft radius, dex save for half
7d6, 5ft radius, dex save for half
8d6, ray of fire, ranged magic attack