Subclass specific quest lines that also increase power.

Goddangit, I thought this actually was real.

Do you need to use up skill points to bring the skill up to level 30?

No

Slash Blast doesn't lose damage on multiple mobs.

I mean like, when you use slash blast on a mob, the damage goes
2500 -> 2100 -> 1700 -> 1100 -> 800 -> 400 it weakens after every monster it hits.

instead of that crappy formula, it'd be like 1700s all around for even distribution.