Dynasty and NYXL are both well-rounded teams that have stars up and down their lineups and the classic Korean team-first mentality that has helped catapult Korea to the top in esports. Dynasty have demonstrated the most poise under pressure, which is why I'm giving them the edge, but NYXL's dps line, even without Flow3r, is unreal.
Spitfire have an incredibly talented roster, but I don't think their team cohesion will be quite as good as the top two. If they can manage to overcome the complications arising from having two distinct teams on their roster, they can win the league.
Fuel are talented, but over the course of a long season I can see them breaking down. Maybe it's just because I'm personally biased against Taimou (he's a great player, but there's no denying he's not a nice guy), but I feel like they won't be able to sustain success against the top teams, especially if they lose a couple matches early on, due to the nature of some of the players. Stamina is an important aspect of s1, and I feel like the Fuel might be lacking that. Of course, they could certainly prove me wrong and do better than I'm predicting, if the team can keep Taimou in check, and it's very unlikely they'll do any worse than 4th. They have the talent, but talent isn't everything.
Outlaws and Valiant both seem to have good chemistry, and while neither of them has a ton of star power, they can both field consistently meta-proof rosters, which should help throughout the long season. I gave the edge to Outlaws because of their tank line, but if Agilities plays well Valiant could be a scary team. Valiant have a lot of potential, but it remains to be seen whether or not they'll meet it. Outlaws need Clockwork to play like TF2 Clockwork, or the meta to shift away from full-time tracers.
Mayhem have a good roster with solid chemistry, but they'll need to make signings halfway through the season if they don't want to burn out.
Gladiators are an enigma to me. On the one hand, picking up Kungarna's tank line might not have been the best idea. On the other, BigGoose really impressed me during contenders, and people really seem to like Surefour.
After watching Mykl's video on Uprising, I feel like they'll at least be alright. Striker will need to play very well for them to win games.
Fusion have talent, but they appear to be an incredibly disorganized team. Hopefully Shadowburn can save them.
Chinese OW appears to be corrupt and filled with incompetent management. I don't expect anything good to come out of China for a while. At least the players probably have had some time to practice together and learn to play as a team.
Shock had better hope Nevix and dhaK can overcome the NRG curse, otherwise, until super turns 18, this team will get stomped on.