It wears quickly if the mob is getting hit, while only useful on most fodder mobs (it actually lands on some RotZ Nms, I haven't seen it land on any other Nms but haven't really tried) it certainly doesn't wear instantly.

Agreed on the second points but SE did say they were looking into it, going back to old areas and finding shit is flat out immune is aggravating. I've had better luck enfeebling Zone bosses than in Wotg...