That is because evil damage type is not programmed to deal different amount of damage based on target's alignment. And those spells are programmed to deal damage based on target's alignment.
So it is spell functioning that makes it work different, not damage type functioning. And they obviously made an oversight when programming abilities that use alignment damage.
They should have programmed the Utterdark Blast (and other abilities that use alignment damage) to give different amount of damage based on target's alignment.
For Utterdark Blast they could have made a different logic than in spells so it does not become completely useless (they could have even made those spells to use this logic):
- half damage for evil targets
- full damage for neutral targets
- double damage for good targets
- no damage to mindless creatures (like constructs) and environment objects (like breakables, doors, crystals, pillars) that really do not have alignment in a classic sense
Evil damage should do damage to everything. It's evil after all.
How exactly would evil alignment mobs damage each other if their damage type didn't effect each other? Sing the kumbaya song, because evil guys are all buddies?
Doing this would pretty much Nerf warlock to ground vs current lock, but probably how it should have come out. My suggestion when it was in early development was to have the save based on shape instead of pact. Imagine that, a spellcaster adapting to the mob type instead of trucking over everything, oh wait that is what spellcasters do just not locks.