Upgrading skills

[Antagonist]

My build:
Magic missle - Cool down 5
Fire bolt - Attack power 5
Lightning bolt - Effect time 5
Magic blast - Attack power 1

Lightning bolt has additional damage. It's displayed in red text(117 damage in this video).
The damage increases to two times by Empower(2 or 3 points) of Effect time.
However, spending 5 points was useless.

Thanks for the info. I knew Lightning Bolt had an effect, but I wasn't quite sure what it was, so I just avoided adding into it.