I think this game was definitely one of the highlights of the week with a very interesting matchup. Vay brought a very nice balanced team that should enable him to switch seamlessly between offense and defense. Choice Band Dragonite, Breloom, and Choice Scarf Heatran synergize well with a SkarmBliss core, which is further supported by Starmie, which provides spin support for Dragonite and Blissey in particular, a second fighting resist and Infernape check, and Thunder Wave to support Dragonite and Breloom.
Hyoga brought a known AgiliGross Toxic Spikes build that makes great use of Roserade, Swampert, Sub + Will-O-Wisp Rotom, and a Magma Storm Heatran to hopefully support a late-game Metagross sweep. The Swampert set is likely some Choice item variant, probably Choice Specs, which serves to lure in and KO Skarmory. Roserade provides a nice backbone versus Pokemon like Starmie, Suicune, opposing Swampert, and even Gengar and Rotom. Substitute + Will-O-Wisp Rotom is a nice addition to this team, as it can cripple offense by spreading burn and firing off STAB boosted Thunderbolts as well as wear down defensive builds that utilize Blissey/Clefable by setting up a Substitute and near-invalidating these Pokemon in a one-on-one matchup (more so Blissey, which we see in the game).
In terms of how these teams face off against each other, the matchup is probably only slightly Hyoga favored. Vay's team has a strong backbone for Swampert in Skarmory + Starmie + Breloom. Despite how the matchup played out, Breloom is a nice way to combat SubWisp Rotom provided that it's relatively healthy, especially after paralyzing it with Starmie's Thunder Wave. Heatran should be able to take an attack or two from Rotom and find a decent number of opportunities to switch in, especially since Roserade reveals that it does not have Hidden Power Ground. Choice Band Dragonite can serve as great sleep fodder for the Sleep Powder Roserade, and between the double Natural Cure, Rapid Spin, and Breloom's status immunities via Toxic Orb + Poison Heal, this team should be able to handle Toxic Spikes teams decently well if all goes according to plan. That said, the Rotom set is still a menace to face with Blissey, as Rotom can set up every time it gets in on Blissey. Latias has the potential to annoy Vay's team with Trick because it's difficult to absorb the Trick with ScarfTran. Vay's Breloom shouldn't get that many chances, as all of Hyoga's Pokemon should outspeed it and either hit it super effectively or, in Rotom's case, wear it down with Thunderbolt. Having two fighting resists and one immunity also helps Hyoga out in this regard.
In terms of how the actual battle plays out, we see Vay go for an immediate turn 1 Outrage, taking out the Swampert in one shot, but trading with it since Ice Punch Metagross outspeeds it and revenge kills it. Without Dragonite, Vay loses valuable sleep fodder, a potential revenge kill opportunity vs Scarf Latias, and some counterplay versus the Magma Storm Heatran. I think it may have been better to switch into Starmie first turn on Vay's side, as it enables Vay to properly scout Swampert. With Rapid Spin support in the back and a decent amount of Swampert coverage, the trade was likely not worth it. I'll touch more on this later. The battle continues and once Roserade is in, Vay starts to struggle a bit in the matchup, as he now has no sleep fodder and is forced to use his Breloom to combat the Roserade. Hyoga gets an early wakeup and Vay opts to go for a questionable Mach Punch, which leaves his Breloom at 16% HP when it switches out. Hyoga uses his Metagross to lure in Skarmory and makes a great double switch into Heatran, which enables him to put more pressure on Starmie/Blissey. Vay does well to use Thunder Wave twice to catch the Rotom once his Starmie is in, but after he switches Blissey, which Hyoga lured in, Hyoga opts to sets up a Substitute with Rotom and Vay plays from a bad position for the rest of the game. Hyoga can force chip damage onto Heatran, which Vay is forced to use to break Rotom's sub and try to gain some momentum back. The early-game and wearing down Breloom was all Hyoga needed to set up for the Substitute Rotom to wear down Vay's team significantly, keep his hazards, and effectively close out the match.
In retrospect, I think both players brought very solid teams. The early wakeup with Roserade drastically changed this game, as it enabled Hyoga to put Vay's Breloom effectively out of commission for the rest of the game, leading to Substitute + Will-O-Wisp Rotom becoming very threatening. Judging by the fact that Superpower's damage on Roserade was a critical hit and that Roserade was very unlikely to use Sleep Powder, I think using Mach Punch on the weakened Roserade was not a great play. Switching into Heatran, which should be safe, would have enabled Vay to use Breloom later and potentially gain some momentum against Hyoga's team. I also think Starmie may be the better choice to lead with, as the team has a solid backbone for Pokemon that force Starmie out, and it doesn't force awkward trade scenarios with Choice Band Dragonite that Vay's team can avoid. Hyoga played really well overall, and is poised to do very well this SPL. Vay for the most part played decently and played his outs when he needed to. I think Vay will definitely bounce back and do great as well, as he has shown that he is a great DPP player and a talented builder.