Zargerth

He has Skarmory on Normal? To be honest I can't say I agree with this change. Sure, Drifblim dying ASAP might allow the rest of his mons utilize Tailwind, but Skarmory brings important resistances which the rest of Souta's team lacks like Rock (due to Strong Wind) and powered-up Flying. 

The problem with only one Tailwind setter is that it's relatively easy (at least for me it was) to stall long enough for Tailwind to die out. I suppose that's just the power of dual screens. The big hitters like Braviary or Pidgeot either got outsped or tanked by A-Raichu and Metagross respectively.

Edit: I forgot to add that in my opinion that Dragonite is his weakest link. Fire Blast is nice Steel-coverage, but other than that it fell pretty flat.

Well, it was a highly offensive skarmory- it seems to me like most of its investments went to Attack and Speed, which combines with the Defense drops to make it fairly squishy for its kind. It isn't intended to stall like most builds, and packs Steel Wing just in case you decide to try and stall it out with Rock Type despite the weather (though I suppose Alolan golem would be able to put it in its place pretty easily). Besides, it makes skarmory weak to Fire, which can come in handy for some people!

As for stalling out the Tailwind... I tried that the first few times, to be honest. It... really didn't work so well (largely due to how frail most of my team is, admittedly). Even once his skarmory fell, he had his swanna come in and clean things up- it outsped a good chunk of my team after the Tailwind petered out, much to my chagrin. It took me a good number of tries before I got to see is Mega Pidgeot, and that's with a good few strategic adaptations (and Revives). I was pretty much forced to use the Seed strategy against him just to stand a chance! And even then, it still took me a few more tries. (It probably doesn't help that I didn't remember that Mega Pidgeot's Ability is No Guard until after I finally won- I had been playing it safe by using Poison Jab instead of Gunk Shot, because missing would've spelt disaster for me).

Going back to your first post though, I don't think gliscor would've been too effective on his team. The Sky Field completely negates Earthquake and Bulldoze, meaning that it would either get stuck using its less-than-stellar Special Attack (Hidden Power, Earth Power, and Mud Slap) or the not-so-good Sand Tomb just to have access to that STAB without changing the Field. It can change it to the Mountain Field on its own via Smack Down, of course, but that removes the benefits from Sky Attack and Hurricane indefinitely, ultimately weakening Souta's whole dynamic. Don't get me wrong, gliscor's a pretty cool pokemon, but it simply isn't something the old man can make good use of...

Sturdy guarantees Tailwind without the seed or anything, so offensively oriented mon like that Thundurus could perhaps make better use of it. In my experience Souta needs another mon for setting Tailwind again.

I guess it depends on your team composition what kind of approach or strategy works. My Metagross has HP and Atk EV investments so it can take a few hits. My Lunatone also has HP EV investments, it resists Dragonite's Fly and Fire Blast not to mention it has Moonblast for dealing super-effective damage. This Dragonite is leagues easier to deal with than Dragon Dance variants.

I wasn't thinking of Ground-STAB when I suggested Gliscor. Even if it can't use Ground-type moves, it still has access to moves like Sky Attack/Acrobatics and Tailwind. Gliscor also boasts nice physical bulk and useful resistances, it's weak to Water and Ice only. Then again, he already has Thundurus for negating Electric-type moves as well as Braviary for Sky Attack spam. You might be right on that Gliscor doesn't work for Souta all that well.