This thread just got resurfaced the day after I read a chapter from Hope Jahren's "Lab Girl," and I had an "aha" moment about the "sacrificial plant" observations. Many people have observed that one plant gets hit harder than its neighbors and assumed it's weaker, but I'm wondering if it was simply unlucky.
In her book, Jahren talks about how plants communicate- through roots as well as through VOCs, and I'm wondering if the sacrificial plant was the initial bug target, but as soon as it got attacked it started signaling to neighboring plants that they should up their bug defenses.
So it's not that it was weak, it was that it was first, and the other plants are doing better because they got a warning shot.
I highly recommend "Lab Girl" for anyone interested in plant biology, chemistry & evolution- it's beautifully written as well as being hugely informative.