I cba to re-write it but its my first reply to this
As for WD+5000 vs WD+100%:
Your weapon needs to have an average base damage of 5000 or higher for +100% to be better, this isnt the case for many many weapons
As youll find from the above link, +affixes are applied AFTER calculations, same here, your damage will be increase by the epic +100% or the legend +200% THEN the +5000 will be added. But the weapon damage is calculated before anything else so +5000 WD is my go to.
The mythstone ‘endow’ gives +50%WD, this is additive to the +100% WD for 150%, (not 2x1.5-1=200% or 3x1.5-1=300%) making it only viable if your weapon has a base damage of 10’000 or more which never happens
By base damage i mean the weapon at +25%item quality, level 100 with NO affixes, just the raw value