Well, from a tabletop standpoint it should be either Divination or Necromancy. Seeing how they have destroyed the core of Necro (animate dead), I'd say Divination. Moreover, Wizard played as damage dealer is (and always be) subpar and, regardless, Evocation school was never that good anyway.
That's irrelevant here though.
Larian let you double Fireball with Haste (or "surprise attack") which alone sweeps all balance out the window and makes that the most powerful thing by far that you can do. One-hitting enemies with damage before they even get a turn is a thing in BG3.
They also let you do
double damage with Lightning and Cold spells just by making enemies "Wet" first. Again, ridiculously OP in favor of blasting away.
They also crafted an amulet that pushes Magic Missile damage to be OP. I don't see an amulet that increases your Enchantment spell DC's by +2 or increases your Sleep potency. What I do see is Sleep getting nerfed hard, and Minotaurs completely ignoring my Sleet Storm by making 60ft. jumps over it.
They nerfed all forms of battlefield control magic, as I described in my previous post. See a pattern here by this developer how they (not so subtly) encourage you to play?
So, Evocation is in fact by far the most powerful and nothing else comes even close. I can only hope they pay attention to these forums and see how they're ruining their own game pushing a certain playstyle so hard and eliminating others in the process.
