Rank 3 might not be quite as awesome as it sounds since it's just adding a % to the BASE damage if anyone needs to free up any advantage points
I noticed something peculiar tonight:
My 605 damage shadowblast was only rising to 834 while in shadowform; an increase of about 38% as opposed to the 72% it said on shadowform's tooltip. So I investigated and believe I found the solution.
My base shadowblast damage before advantages, before superstat increases, before shadowform was:
Advantaged to rank 3 it was
Plus my superstats of +18% each it was
Plus shadowform 72% it SHOULD BE 1,040. It was
So why did I only get a 228 increase rather than the full +72^?
Well if we apply +72% to the VERY BASE damage of 318, we get +228.
228 + 605 = 834. Bingo!
Damage buffs such as sheaths/shrouds, forms, and buffs such as the one given from force eruption advantage or spells only appear to be affecting the very base damage, unranked version of the spell.
The devs explained long ago that the damage bonuses are additive, not multiplicative.
If you stack Shadow Shroud III (+48% damage) with Shadow Form III (+84% damage), your damage is calculated as [Base * (1 + .48 + .84)], not as [Base * 1.48 * 1.84].
Defensive bonuses work the same way. 50% mitigation doesn't mean you take half as much damage, it means it adds .5 to your defensive divisor.