if i go infernal collapse for example, does fire dmg +20% boot its dmg?

This post was edited by Doppelganger on Sep 24 2012 02:20pm

+% to elemental mods work on spells of the listed element, the sum is just not displayed on the skill tooltips. If you press J and check your offensive stats you can see the totals of each.

and what about xx to fire dmg? that is added too?

Without a % indicator I believe it only adds that damage to your basic attacks, but then that is modified by your % modifier. It's a little confusing and unclear unfortunately.