How does "elemental" damage on weapons work with "physical" skills?

Suppose I have a weapon that does 1000 (black) damage and 1000 arcane damage, and I use it with a skill that says "Physical" in the skill tooltip. And I have some gears that says "Physical skills deal 20% more damage".

From the animation of how monsters died, I noticed dead monsters have a glow of arcane color on them, suggesting they were killed by an arcane damaging source, even though all my skills say Physical on them. This made me concern about whether "Physical skills deal 20% more damage" is actually useful.

I then did an experiment with a friend in the PvP (brawler) mode. My friend equipped an amulet that prevents arcane damage and heals herself instead. I then used that said physical skill with my arcane weapon on her - and she took some damage and healed some, suggesting my "physical" skill had a physical component and an arcane component.

Does anyone know how exactly the damage is calculated? Specifically, is that "physical skills deal 20% more damage" working to its maximum?

• Short answer: most physical skills don't alter weapon's physical/elemental fractions, hence +physical bonus only affects a portion of the damage. There are some physical skills, though (mostly Monk's), that explicitly convert weapon damage to Physical, like elemental skills do. Let's wait for someone to answer properly with a list of those skills. Commented May 27, 2014 at 18:47
• @OrcJMR Thanks. As I have tested, the physical skill I was using clearly had been split into two components, but the wording of the bonus gear is "Physical skills deal 20% more damage". I wonder if that skill is still considered a physical skill. If the wording had been "Physical damages are increased by 20%" then it is probably only working on the physical component. Commented May 27, 2014 at 18:51
• well just as a quick test I took my WD's pets out for a spin. He has a doom bringer with 2259 average dps (out of which the majority is cold) which I swapped with a thunderfury that has 2230 average dps (out of which the entire damage is black) and my pets do significantly more damage with the doombringer due to its +17% physical skill damage modifier. So at least for fetish army, its converting my weapon damage to all physical for the calculation.
– l I
Commented May 27, 2014 at 19:19

Physical skills work a little bit differently than Elemental skills. Here is my current understanding of the difference:

Normally, using an elemental skill (e.g. arcane) will convert all of the damage from the skill to that element. It will then be modified by stats like "Arcane skills deal 20% more damage."

Here is a semi-official post regarding how this works:

Physical skills work a little differently. Some physical skills convert damage to the physical type, some do not, and some only convert some damage to physical. If you have a weapon with elemental damage (e.g. arcane), these skills may still allow the arcane damage to go through. The physical portion of the damage will be affected by the stat "Physical skills deal +XX% damage," and the elemental portion off the damage will be affected by elemental booster/immunity stats, like your friend's amulet.

I do not have an official source about physical skills, but here are some discussions:

Here is info on how to tell if a given physical spells convert damage type to physical:

Unless a skill explicitly states in its tooltip that it deals Physical damage it will inherit your weapon's element. For Elemental bonuses this means that some of the skills that are listed as Physical will actually receive an Elemental bonus that depends on which element your weapon carries.

For example, Multishot / Full Broadside is listed as a Physical skill, but it actually doesn't have an innate element. As a result when I use it with my Cold damage Windforce its damage is increased by Cold elemental bonuses.

I cannot find any official confirmation that this is true for all physical spells that do not literally say "physical damage" in the tooltip, but it's the most definitive answer I've found so far.

• I don't suppose you've found a list of which skills convert and which doesn't yet?
– l I
Commented Jun 20, 2014 at 1:41
• @z' I do not have a list, but I found and added a promising link on how to tell. Experimentation might be needed to confirm it. Commented Jun 20, 2014 at 5:15