skeleton shield and permafrost shield are effective ways to deal with immaterials.
Quintessence is here to have a bit of breath from all the rains of bolts and fire that are in the battlefield!
Currently mass CC actually target all of the creaturs, going in the slot number order.
It
hits creatures in slot number order, it does not target. "Target" as defined for Elements is the aiming crosshair that shows up if the spell or ability is a 'targeting' type. This is why SoFr gives avoidance to air creatures if the spell or ability pops up the crosshairs requiring a target before the event/action triggers. Also, T-storm, Rain of Fire, Pandemonium, and the like ignore any avoiding effects of SoFr before they do not have to go through the targeting code / actions.