Hey, we played the deck so I get it. Also, you are a much, much better Pokemon player than we are, so maybe we are just wrong, but I have to say: Your story is much the same story we were telling ourselves. Unfortunately, I think the deck performed for us in a way that demonstrates that it is good, but not amazing - and unfortunately, to win, you need amazing. We thought 2, 3, and 4 were true for sure. And I think it kind of works out like that in practice, but the less reliable T1 lock and the much lower initial damage output seemed to offset these benefits.
We tested Korrina and as our list indicated, we ended up cutting it for other supporters because we found that we were rarely one piece away - we usually needed to just keep digging into our deck further to hit the T1 lock and the Korrina did not really give us enough to justify being our supporter for turn when we were trying to set the lock up. For example, a good T1 for us consisted of getting out a Carbink, getting an Oddish/Gloom/Vileplume, getting one or two other attackers on the board, and the FGP. Further, we would like to attach an energy, attach an FFB before the lock comes down, and have a plan to get the Carbink Break out given that we won't be able to Ultra Ball for it going forward but Power Gem is usually important. Given the volume of pieces we felt like we needed, Sycamore seemed important.
If your point is that Zygarde Vileplume is good and we just played it poorly or had bad variance, that may be true. Determining how thinks work in Pokemon is hard, so all of my opinions seem more "feeling" based than quantitatively data driven, so I accept that I could be wrong, but I FEEL like the deck is just ok.
Thanks for the commiseration. Worlds is hard! Congrats on your great Day One run!