Hello again, TOSC, a team's never too perfect, so I'll be helping you build this team all the way!
The team looks much better, and although I cannot playtest it myself, it still seems to have a weakness to Earthquake DD Gyarados. Empoleon has to come in on the DD, but can't do anything except die to Earthquake. Luckily for you, most Bulky DD Gyaras (Offensive Gyaras are hard to come by, it seems) run Dragon Dance / Waterfall / Stone Edge or Bounce or Return / Taunt. This attacking combination is only resisted by Empoleon and Shedinja in OU. It is also worth noting that Hippow can just continuously Roar, switching in on the Dragon Dance and taking the next Waterfall and rack up more Stealth Rock damage. I'm just warning you of a mild threat that can come by for a late-game sweep. It's also especially dangerous when Scizor is locked into anything not named U-Turn.
Offensive Suicune is also giving this team a hard time. Any 4/252/252 Timid Suicune with Leftovers and Calm Mind / Surf / Ice Beam / HP Electric can cause pretty big damage to the team. With Leftovers, residual damage won't be killing him, Empoleon's HP Electric 2HKOs after Stealth Rock while he outspeeds and 2HKOs your Empoleon with his +1 HP Electric, meaning he wins that matchup, and he'll OHKO Hippowdon with Surf after Stealth Rock before you can Toxic him. Although there is a solution in smart switching, it still guarantees one of your pokemon will be down and out.
IMO, the best remedy to this might be to switch Hippowdon out for another phazer like Zapdos, Vaporeon, Skarmory, Latias, or Heatran. Zapdos, Skarmory, Latias, and Heatran all give a nice Grass resist, with Zapdos and Heatran being able to counter Celebi and Rotom-A, and Latias also provides Wish and Reflect support, potentially opening up a slot in Jirachi's place (or Latias for Jirachi could work too), and Skarmory can set up extra entry hazards in the form of Spikes, but having a random super-defensive pokemon slows your momentum of battle, which is something this team definitely does not want; but he still is worth considering, given him immunity to Sandstorm and an extra Taunter (should you opt for Taunt > Brave Bird). Suicune's +1 HP Electric breaks even Specially Defensive Skarm, so that doesn't help much. Suicune's Surf hits Heatran pretty hard, but if Heatran comes in on an Ice Beam or the CM, he can survive it, phaze out, and use Rest or switch out (however, with Wish support, Heatran can run a nice Defensive set). Specially Defensive Zapdos is an excellent check to Offensive Suicune; I mentioned Heatran and Skarmory for their Sadnstorm Immunity and neutrality to Stealth Rock, as that may appeal to you more than Zapdos' weakness to the latter and the former. Although Suicune's Ice Beam hurts Zapdos, Zapdos' access to Light Screen allows him to effectively stall out Suicune, as Suicune's lack of recovery cannot shrug off STAB Thunderbolts from 286 SpA. Here's a set I would like to see you try out:
Zapdos @ Leftovers
Pressure
Calm
248 HP / 224 SpD / 36 Spe
~Thunderbolt
~Roost
~Light Screen / Roar
~Toxic / Hidden Power Ice / Roar
This set allows you to either Toxic stall or even PP stall Suicune's attacks. However, if you would liek to outspeed Suicune (as Zapdos is still 2HKOd by +1 Ice Beams), then you could try a speead suited for doing so. If I'm not wrong, I believe you just need 240 Speed EVs and neutral nature to outrun it, but that severely dents walling capability; but it is your choice (it helps in Toxic stalling). Zapdos also helps compensate for Bulky Gyarados that run Earthquake instead of Stone Edge or Return and even Ice Fang offensive Gyarados. I know my logic seems hypocritical at this point, but it seems you don't absolutely need Roar, but if you still wish to have a solid phazer, Zapdos fills the role quite well.
Might I also point out an Offensive Celebi weakness as well. A Celebi with the set of Calm Mind / Grass Knot / Hidden Power Fire / Recover holding the item Life Orb with the EVs 76 HP / 252 SpA / 180 Spe and a Timid Nature can actually tear this team quite badly. Celebi can set up on Jirachi and Empoleon and hit everything on your team hard. Gliscor is 2HKO'd by +1 Hidden Power Fire after Stealth Rock and his only attack, Earthquake, can do almost nothing to Celebi. Empoleon is just set up fodder. Jirachi is hit hard by Hidden Power Fire. Tyranitar is obviously shattered by Grass Knot, as is Hippowdon. Scizor can Bullet Punch before going down, otherwise HP Fire is an OHKO.
Once again, Zapdos can remedy even this! Grass Knot and Hidden Power Fire do absolutely zero to the suggested spread, and with Toxic, Celebi is doomed, even with Recover. Super residual damage ftw. Heat Wave isn't suggested here because if Celebi boosts to +3, Heat Wave does an amount where Celebi can attack, take LO recoil, take SS recoil, and a Heat Wave and Recover all of the damage off, which is something Hippowdon can't do even at +3 SpD.
All and all, I highly suggest you at least test Specially Defensive Zapdos to keep momentum in your favor and do not lose it at any point. That is my reasoning for not using Blissey, as a random wall on a team like this just ruins all flow and loses momentum as they bring out their MixMence, MixApe, or SD Luke and set up or OHKO Blissey and gain momentum.
That's all I've got for ya; look at how far the team has come. It's got a lot less weakness, but there are some glaring weaknesses still, such as the ones I've mentioned.
I hope my help helped! Good luck with the team!!
