Actually, a really good Deo-S set is
Deoxys-Speed @ Leftovers
Ability: Protean
EVs: 4 HP / 252 Atk / 252 Spa
+offensive - defensive nature, idk
- Psycho Boost
- Super Power
- Ice Beam
- Knock Off
This set actually works really well since Deo-S outspeeds every threat, anyways.
A Nasty Plot set could work too I think
Deoxys-Speed @ Life Orb
Ability: Protean
EVs: 212 Spd / 252 SAtk / 44 HP
Timid Nature
- Nasty Plot
- Ice Beam
- Thunderbolt
- Hidden Power [Rock] / Shadow Ball / Hidden Power [Fire] / Superpower
The spread outspeed scarf base 100's. However, you can run a Modest set with no speed if you want, as no speed DeoS outspeeds unboosted base 130s. Boltbeam + Protean is really cool. HP Rock is for Wonder Guard mons. However, since they will most likely be banned, Shadow Ball or Dark Pulse are better options in the last slot. Hidden Power Fire is also an option. You can even opt to run Superpower and put those 44 into Attack instead.