Ah I see how about elemental critical does 100% is enough is it really 100% proc? Often I go beyond 100% like 160% elemental crit does 60% extra crit goes waste?
The cap is 40% in stats page so anything above that is a waste as I have tested for myself. But even something as high as 30% is more than enough depending on how fast you attack or the dots and stuff. With epiphany (5), you can get 50% elemental crit though.
Also I remember coat skill used to be able to do 100% crit chance and 100% elemental crit which disregarded the caps but thats changed to 25% or so and follows the caps.
You can use Ignore resist but better to use 100%+ weaken to double dmg and also defeat immune enemies and enemies that resist very much.
Weapon + and % only affect the weapon its on. Elemental damage affects both weapons and is global damage. Can be placed on any gear. Also WD*ED does happen in dps formula for both weapons and is the major damage that gets multiplied by sets, affixes and skills. So Elemental damage is the major damage and worth having ED% which multiplies BWD of your weapons.
Cap for Elemental crit dmg is not there for things like Frostbiting 100% but there is cap for elemental crit chance which is 40%. So in theory you could have up to 1200% Frostbiting and get away with it assuming you used all eternal or 600% without using eternals combined.