First off, it applies to all elemental damage whether it's from a spell or attack. The penalties/bonuses do not stack with multiple hits. Chaos is not an element, fire, ice, and lightning are the only elements. The way multiple elements at once work is that the penalty is applied to all the elements you hit with on the previous attack, and the bonus to the ones you didn't hit with on the previous attack. So if you hit with both fire and ice, on your next attack fire and ice will BOTH have penalties, but lightning will get a bonus. If you hit with one just one element, only it gets penalized, while the other two both get bonuses. If you hit with all three, all three will be penalized on your next attack.
The penalties and bonuses last for 5 seconds, or until they are overwritten with a new elemental equilibrium strike (ref). When soloing each of your hits will reset the resists/bonuses based on what you hit with.
The changed resistances will apply to all damage dealt to the target, whether it comes from you or your allies. However, only hits from you or your traps/mines/totems will trigger the effect - so you could for example attack with lightning damage to apply the effect while your minions or party members attack with cold and fire damage to make use of the lowered resistances.
Let me preface, I've played hundreds of hours on hardcore only so my views on crafting differ widely to softcore where there is no removal of items for the economy.
When should I wait and when should I create?
Wait for high ilevel items, lvl 56+ is usually a good place to start. The reasoning behind this is to make sure that your not wasting currency on low level rolls.
When should I pump it and when should I lump it?
Highly subjective, generally a good rule of thumb is to look at the possible max rolls, if you have a high potential max roll and you have a low actual roll then go for it.
When should I buy it and when should I apply it?
Easy buy currency low and sell high, play the market. Selling 1 exalt today might make you 1.1/1.2 exalts tomorrow (exchanging chaos).
When should I damn it and when should I spam it?
I assume your talking about high level items/uniques. In that case always watch the market, keep an eye out for new builds that rely on certain uniques and make your money there.
When should I whet it and when should I forget it?
Whetstones and Armour Scraps are dirt cheap (look for the 40% vendor recipe). Always max your items out. There's no need to be running around without 20% everything. Also worth noting that white items get 5% per consumable apposed to 2% magic (I think) and 1% rare.
When should I hone it and when should I disown it?
Hone always, discard rarely. In any league your characters will greatly benefit from your hand me down gear. Also there is a real market for twink gear if you have some nice pieces.
Hopefully that should help!
Best Answer
Well, you do know that EO is a 40% multiplier. That will result in 1.4 times the damage. The numbers in the table are the multiplied base damage by certain critvalues.
Any value you see in that table that is under 1.400 (times your base damage) is less damage then just EO damage. So RED is where EO has higher value.
Still you can not just look at crit vs EO in a vacuum. It depends on so much more. For example whether your skill can even crit, if you do 100% of your damage as elemental or are you doing some of it as physical or chaos or if you can profit from different rolls on gear that will make gearing for crit extremely hard or even not worth it.