I think you nailed it Staffan Johansson. Everything starts out really strong with Magic Missile - auto-hit, force damage, up to five different targets. Things are pretty good into the mid levels, but then the direct damage spells start to really regress. Polar Ray? Seriously? Exact same as a cantrip except for max damage? Ice Storm and Shout have potential, but they both max out at 5d6, which is already a little weak when you first get access to it, then becomes total fail within a few levels.
I don't think ignoring SR or energy resistance is a good solution, they are balanced and integrated into the game fairly well. Increasing the dice to d8, d10 etc. will have a fairly minor effect.
In general, I would like to see more acid, sonic, and force damage, longer ranges, and more targeting options for the higher levels of evocation. I would propose making spells like Shout and Ice Storm scale with caster level. A spell like Polar Ray could fire a ray/3 caster levels, and still not be over-powered.
I would say that the school of evocation is OK, but there are a half dozen or so of the mid-high level direct damage spells that need to be scaled for higher level play. (Same as most of the other schools)
I am considering raising all caps on spells, but at a slower rate. So fireball caps at 10th CL, but I was thinking about every 2, 3, or 4CL afterwards might raise the max by an incriment. So, I am thinking about 4 the most, but haven't gotten to test this at all, so even 2 might work well. Assuming 4 CL's, a 20th level Wizards fireball would deal (unmodified by anything else), 12d6, and 13d6 at 22nd level.
Now, this wouldn't solve all the problems with direct damage, but it may help. For Magic Missle, a sort of special case, I might allow more Magic Missiles, but each one after the fifth must target a creature that has already been targeted.
Another thing that might help, is to allow Area Spells to Crit, in a sense. Something like if you fail the save by (lets just say) 5 or more, double damage. Maybe 10 or more if thats to strong. This is a little more WoW than I'd prefer normally. . .
I'm starting to think that maybe 5th level spells should do d8s, 7th level do d10s, and 9th level do d12s or something. That would give direct damage some interesting scaling with spell level, not just caster level.
I like this suggestion. It helps direct damage magic to scale without overshadowing non-casters. It helps to make direct damage a more viable option but still leaves the Arcanist's niche alone so that save or suck casters don't feel sub-optimal relative to direct damage casters.