"They're attempting to define a generation around a shared experience or event."
What you say here is correct; "this generation" (Matthew 24:34) is clearly such a definition.
"The 'World War II' generation is a good example of this usage."
Actually, Tom Brokaw (NBC News) called this generation (no pun intended) "the Greatest Generation." I'm agreeing with you here, too.
"The problem is, this doesn't work unless the event is fairly short in duration."
Nonsense. I'll just stop here. If you should decide to respond, please take as long as you need. This is conjecture on your part and it flies in the face of the truth. What truth do I mean? Read on.
You provided the Greek word _genea_ [Strong's G1074] used at Matthew 24:34, which is rendered "generation" in most English language Bibles, but which can also be used in referring to a period of time, like, for example, the Dark Ages, also known as "the Early Medieval Period," which encompassed several generations, from, say, 500 AD to 1000 AD (I'm approximating the dates, but I'm sure you are getting my drift here), which was followed by the Middle Ages, also known as "the Medieval Period," which also encompassed several generations, from 1000 AD to 1500 AD, which was followed by the Renaissance, which covered about two centuries from 1500 AD to 1700 AD. I think you can see where I'm going with this. Read on.
You wrote "May 15th, 1984 WatchTower articles ... as absolute PROOF of 1914 and This Generation," but I don't believe this issue to be the one you intended, so would you please check this reference.
I'm absolutely certain now, if I wasn't before, that the phrase "overlapping generations" will either be fleshed out some more or just dropped, since I've read many of the posts here and now I don't see how the use of this phrase is going to be all that helpful to those that are wrongly construing the paragraph in which the word "overlap" is used to describe Christ's anointed brothers that not only discern the composite sign, but live contemporaneously to its manifesting itself from 1914 to the period when the great tribulation has begun. A couple of quotes that are pertinent to this topic are as follows:
"As a class, these anointed ones make up the modern-day 'generation' of contemporaries that will not pass away 'until all these things occur.'" ["Christ's Presence-What Does it Mean to You?" (w08 2/15, p. 24, ¶15)]
However, nothing that you have read in the Watchtower -- ever -- has said a thing about there being two generations, let alone that the Bible supports the combining of "two generations as one."