the "all enemies" qualifier just indicates that it hits everything in its path that isn't an ally. neutral NPCs are considered potential targets for aoe spells for the reasons i stated above
For Dust Blast, the description already state it only attack enemies (not related to aim skill). You can check my edit 2 in my first post, Dust Blast behavior is not consistent with Pyroclastic Eruption (edit: added Earthquake too). How would you explain this?
BTW, attacking neutral NPC with these skills will turn them into enemies in various fight.
