The whole metagame forces me to use something specific. The whole metagame should be banned LOL.
Jokes aside, have you not ever considered Rain broken ? It's the most broken thing I can think of. Sun can be countered pretty badly by Tyranitar, but Rain is pretty hard to counter. If even possible.
Laugh away, yes I do think Rain is a bit broken.
*insert Grass-type with Sunny Day* Rain & Sand countered.
I know better than anyone that it takes more than that but in all seriousness, Sunny Day stop Rain teams harder than anything in the game. Not Sun teams, not Ninetales, just the move Sunny Day. Give Rotom-W Sunny Day & HP Fire & you'll see what I mean.
But on the actual topic of Deoxys-S, there's really nothing I or anyone could say that hasn't been said already but I'll give it a crack. Deoxys-S hasn't brought back the lead metagame, but it has brought back the concept of Anti-leads like FS Lucario & Mixed Dragonite. While I do like that and hope that Pokemon like Azelf, Uxie, Aerodactyl, & even Deoxys-D do make a comeback, there's just no way that's going to happen until Deoxys-S is gone. It pretty much gets guaranteed Dual Screen, SR & 1 layer of Spikes, a 140 BP STAB attack off to OHKO a lot of Pokemon, Superpower or HP Fire for just about everything else.
In truth, just about everything that could stop Deoxys-S from doing what it wants for the first 2 turns is OHKO'd by Deoxys-S. Every single reason that Deoxys-S was banned in 4th Gen, still stands today. It may be a new game, but NOTHING has changed about Deoxys-S. Not a damn thing. You can stop Deoxys from doing one thing, be it Screens or Hazards, but you're not stopping both & certainly not without losing a Pokemon.
Is Prankster, Espeon, & the improved Magic Coat enough to keep Deoxys-S in OU? Hell no. The thing is, as far as Deoxys-S is concerned, that is ALL that changed from 4th Gen to 5th Gen. Scarf Terrakion? Scarf Infernape. Deoxys-S is still not impressed. The only thing that can't really be compared is Scarf Zoroark disguised as something like a Ferrothorn. That's about the best all-around counter to Deoxys-S out there assuming it can provoke a Taunt or Dark Pulse flinch to make Deoxys-S waste it's 1st turn.