Honestly, I feel like FNC could take first seed....I mean tilting and upsets have to happen, right? It can't just be the strongest teams on paper/reviewing previous plays. Look at Worlds last year, and IEM Katowice back in March (The Flash Wolves, Team WE, GE Tigers).
I feel like Fnatic is underrated by most casters and analysts for some reason, even after the impressive performance they put up at MSI...And they've gotten better since then.
I do realize that the 18-0 record may not be that impressive considering EU is a weaker region than Korea and China (The analysts and casters say that Fnatic's weaknesses are in the early game, which is something that some teams in EU did exploit, but they just couldn't close games fast enough and misplayed mid/late-game so Fnatic came back and won the game.
Basically, what I'm trying to say is I'm not saying Fnatic is the best team at Worlds, but I don't feel like they're weak either - I feel like they can stand toe-to-toe with some of the Eastern teams, and I think they have a good chance at making Quarterfinals.