For my DT, I know that the coefficient of Covenant of Arms is .25
That lets me know that my +900 magic damage in solo gear gives me 225 extra damage on any CoA procs.
As a result, I was wondering if the Demo had 100 magic damage, does that give a linear increase to spell damage of +100 damage, or does it have an associated coefficient like the DT?
I will be at a level soon where I will have some gear and can run some tests of my own, but was curious just how important +magic damage is (on the DT some abilities are +.05%, so they are relatively useless in terms of significantly increasing damage through the use of + Magic Gear).
I am pretty sure it has an associated coefficient just like the one you have on CoA on your DT. What the coefficient is I don't know.It is definetely not a 1:1.
But remember Bonus spell damage is not your only source you use to increase your DPS.
Critical rating is really important on a demo. When spell weaving you only get 10 secs. of automatic crit. So you really want to prioritize that in your equipment more so than your bonus spell damage.
Base spell damage is not entirely useless on a demo either. Demos have quite high bass spell damage on their spells. So you will actually feel an increase.
Critical damage rating is a bit more in the unknown for me but it definetely doesn't hurt and should be consideredd when deciding what gear to use (have in mind that will of the sublime increase crit dam. rating in relation to intelligence).
But to return to your original question, it should be quite easy to test. Use SW and take max damage and try 2 different gear setups.