In addition, there is also an additional damage scalar that I implemented some time ago. This applies to most damage spells, but not all of them. The missile storms are excluded due to how they divide damage into multiple hits, and I don't think it does much, if anything to the persistent AoE spells. In addition, both Avasculate and Darkbolt have specific caps in place to limit their single target damage potential that is not bypassed by this damage scalar.
Specifically, Avasculate cannot do more than 200 damage, and cannot bring any target under 50% hp. Darkbolt cannot hit a single target for more than 75 damage.
Otherwise, damage is added outside of and beyond the damage cap of the spell. It scales up based on the caster's Caster Level as follows:
Level 5: 2d6
Level 10: 4d6
Level 15: 6d6
Level 20: 8d6
Level 25: 10d6
Level 30: 12d6
A further note on spell damage caps:
It is my intention to increase the damage caps on all Evocation spells based on the Evocation focus feats possessed by the spell caster. (Regular/Greater/Epic). At present, most Evocations stop at 10d6, though some get up to 15 or 20d6, entirely neglecting any epic caster levels, and generally leaving Evocation spell damage as a poor substitute for buffing yourself and swinging a sword around. Personally, I think a Fireball from a level 30 mage, or say... a Lich, should be more cause for concern, and thus when I have time to go alter every Evocation spell script, it will be.