Elemental Damage, along with +skill damage and Increased Damage to Elites are very valuable stats, but are also much understood. These bonuses were very undervalued early in RoS, partially since they didn’t show up in the Character window or DPS display. Then as more and more players caught onto the bonuses, and once Blizzard hotfixed them into the Character window they seemed to become overvalued, with some people making all sorts of DPS sacrifices to add another 15 or 20% damage to their chosen type of elemental damage or favorite skill.
Is that wise? Sometimes, but not entirely. Adding Elemental Damage is great, but it has diminishing returns due to how the formulae are calculated in Reaper of souls, and this new short video tutorial by Such Stronk does a great job explaining how and why.
The takeaway is that sure, it’s always better to add more elemental damage. But that’s never an option in a vacuum. In real situations you’re almost always looking at trade offs, and due to how the formulas work in the game, you’ll do more damage with (for instance) 2 elemental damage affixes, 2 skill damage affixes, and 2 elite damage affixes vs. 4 or 5 elemental damage and 1 or none of the others.
If you’ve already got 60 or 80 elemental damage, you’ll get as much or more benefit from adding 15% damage to your main skill, than you would adding another 20% elemental damage. As always, math is not your friend.