Okay, your post is lots of text and no reasoning at all. The reason why the group with Fnatic might be the strongest, is because the top teams from China and POSSIBLY (well, not Koo, but KT) Korea are capable of playing at the Fnatic level. Meaning there are 3 equally strong teams in one group, and THAT'S what makes a real group of death. If you take SKT group, there's a possibility of one team playing at their level -2nd/3rd seed from China. Same with China, you take LGD, and at best you'll see Koo (and they have no chance against LGD) or KT.
Just because Origen took Fnatic to 5 games, at best they COULD UPSET one of the Chinese/Korean teams (Fnatic played worst games this split, and that's without a question - even in wins they made more mechanical and macro mistakes than in the last 5 weeks combined, not to mention they are FROM THE SAME REGION. That means they scrim and play against each other a lot, and so they are somewhat used to the playstyle).
Anyway Origen will be relevant ONLY if they get the biggest luck of the draw (#1 NA, Koo from either 2nd or 3rd seed in Korea, and 2nd/3rd seed from China, or even better - AHQ).
TLDR; Only group with Fnatic can provide 3 teams that play around the same level, everything else is easy prediction for which 2 teams leave the group stage.
And yeah, I'm disregarding AHQ, because I watched (apparently unlike you) their games after MSI. They're playing at the NA level (and they'd have serious issues winning it), regardless of how well they did during MSI.