Shadow fire shouldn’t get cooldown

[kevindaze]

I get the point to add cd on lunar fire, so it can be tactical minions cleaner, not damage dealer.

But shadow fire is different, it’s supposed to burst your damage on single targets by mass consuming your embers. If there’s cool down on shadow fire, I don’t think anyone will want to pick it anymore. 
Due to the fact that you can only deal 400 damage on "Single target" every 14 seconds, which is increasing 28.5 dmg per sec. And lunar fire can deal 750 damage on "Multiple targets" every 20 seconds, which increases your damage by 37.5 per sec.

Why the hell will I choose shadow fire if above is the case?