Oh, so your moveset is Psycho Boost/ Tbolt/ HP Fire/ Spikes/ SR/ Taunt?
Yes, it CAN attack the common spinners, but the true fact of the matter is, as was brought up before. You have four moveslots. You're not a Thundurus or a Reshiram, you can't cover everything with one set.
EDIT: And one final note on the DS, the screens don't make the opponent's sweepers immortal. If you're getting swept by a Dragonite or a Haxorus when they have 1 DD (which is what they'll get. maybe they'll get 2), change your team.
Applying that same logic, you're running all three Spinners in OU? Obviously, you change your moveset to what you want to counter. While I do admit that Deoxys suffers from four-moveslot syndrome, it doesn't need to specifically focus on one role. It can set hazards without giving up its ability to revenge kill later in the game. The fact of the matter is, once hazards + Expert Belt becomes popular, no spinner is gonna wanna come in on Deoxys. It's not what it will do that's the issue, it's what it can do.
While you can't do it all at the same time, you don't necessarily need to. People knowing what it will do and forgetting what it can do is what screws them over to Deoxys. All you need is max investment in Sp. Atk, enough speed to outspeed Scarf Landorus, and you can do whatever you want with the rest. With an Expert Belt, you can bluff a lead set so good it's not even funny.
The problem with those calculations, although I'm sure they are correct, is that you fail to take into account Expert Belt and entry hazard damage, which Deoxys is certain to get up. Forretress gets its Sturdy broken switching in, thinking it's a standard lead set. It does to spin, then gets nailed by an Expert Belt HP Fire. Then your opponent thinks it's a standard lead set with one attacking move. You bring in something to kill it before it gets too many hazards up. It then switches out, and terrorizes your team for the rest of the match.