Do you gain anything by just sticking to one tree? I like to mix and match.
Better synergy, though there's some good cross-tree synergy as well. Frost for Embermage, for instance, has a lot of -Resist debuffs in it for the other trees.
The damage on it is a lot higher than that, I can tell you that much. I have no armour reduction, however; I'll try that.
To be fair, I haven't looked into how mitigation functions. There could be some other factor to it. I just know that purple text is basically the game indicating to you that your damage output is rather low. Just a way for the game to show that you need to upgrade without needing you to be on the lookout for low damage numbers themselves, just keep an eye out for purple text.
Just to add, by low STR I mean 13 STR/39 Focus. I did forget that I have +16 Physical Damage slotted on my MH with I think +15 or so damage on the rest of my equipment? Gives me a 52-79/44-51 listed damage range for my setup,
Also, Frost Mage so not sure how Stuns (Hailstorm) or Freeze (Icy Blast) add to this.
Edit: Oh yeah, don't forget Fumble Chance + Fumble Damage Reduction.