When you say, "A lot of the big content producers" - who do you mean? There's Ahnaldt, probably followed by Xaereth, and then there's everyone else. There are certainly some noteworthy less prolific content creators out there but those two are the only two left that could be considered 'big'.
Is it a conspiracy? I feel like it takes more than two people for a thing to qualify as a conspiracy.
Leia is still very new - only a tiny fraction of players have her right now. The "best" team comp may not have been established yet, though I reject the notion that there's a single best team comp. I think it's going to take more time to land on a consensus. Also, I feel like most people wouldn't take CRex out of a phoenix squad. They're way too versatile and useful to just toss them aside to make an already great team a little bit better.
As a final point - Ahnaldt explicitly stated in his testing vs Leia that LV is by far the weakest counter to her, and explained why.
I appreciate that you took the time to upload the video (if that's your video) - more footage is always better imo. Do you have any video of this team on defense vs any other GLs? Jabba? JML? Early testing seems to indicate that those are the two easiest counters for Leia. If having Rex on the team stops one of those then it might be worth considering - otherwise, if you have Phoenix geared, I think he stays with Phoenix.