This is something that came up during the booster draft of fyero's "unofficial" Redemption tourney this weekend.
My opponent attacked me with Army of Simeonites, I blocked with a brown EC and ripped a Plot to discard AoS. Does AoS return to territory at 8/8, or are they discarded? We ruled that they are returned to territory.
I ask because, back in the day, there was a difference between "being discarded" and "about to be discarded". Old healing cards such as Elisha's Bones and Bread of Life were worded differently because there was a difference.
AoS - "Each time this character is about to be discarded, return it to territory with abilities decreased 3/3."