If you are running PE and you have your Fire/Storm Elemental out, if your 2 piece procs it extends the duration of the Elemental, but if you are not running PE and your 2 piece procs it will drop a 2nd Elemental it does not extend the duration.
If PE is an 80% buff to the base Fire/Storm Elemental wouldn’t a 2nd non-PE Elementals be more damage? I haven’t tested this but if a regular Elemental is 100% damage and PE makes it 180% wouldn’t 2 regular Elementals be 200%?
It’s like no one at Blizz put any thought into our set bonus other than drop and Elemental and nerf it’s time for PvP.