Well I think your conclusion is a fair one and I'd agree with it. My point though is that your first line of the preceding paragraph may not be accurate and if my supposition is correct then the two are in opposition.
Look I've only been in one guild (well been a long time since I've been in another) and it is indeed a microcosm I can speak about. We were about 105MM- 110MM prior to the SIth Raid. Now at almost 80 MM GP. At our height we did not have 20 JTR teams or close to that. Now I've seen guilds with similair GP take on Heroic. They post about in the forums, but they have a fair amount of JTR I'm guessing. The raid created a bit of a rift (again reading the Sith Feedback Thread for others' experiences) and like in our guild people have been ditching guilds they otherwise were content growing with and in and heading to others that had similair make ups to theirs. Most of those that left had JTR in our guild. Now we have even less collectively. Those that left likely went somewhere that had a higher concentration of JTR already. Again a guess, and to be fair not even an educated one. A wild one.
Also reading through the Sith Feedback 9 or so pages (so this is where I get a bit of reference) Part 1 is the most brutal for a lot of people. Looking at teams they run (as part of the CG question) many don't list JTR. Now there are also a lot that say Part 1 is brutal and do list JTR. Part 1 is a pain for all regardless, but anyways it got me wondering how many people, long time players or not, actually have her. I mean I'm a long term player and I don't. I've slogged through other long farms just fine. I just don't have her because I got bored and burned out farming her.
Just wonderings by me and not supported by any numbers what so ever, just trying to tie some things together, but perhaps reading tea leaves and seeing things that are not there. That being said it's not a wild notion. I'm not sure there are stats on this data to look up and support or refute my idea. Anyways that's all.