Pretty cool set I made a few hours ago, haven't got much chance to test it much but so far it has done quite decently.
Deoxys-Speed @ Leftovers
EVs: 252 HP / 252 Atk / 252 Def / 252 SAtk / 252 SDef / 252 Spd
- Magic Coat
- Stored Power
- Leech Seed
Using it as a lead you spam magic coat against enemy Deoxys-S, or sub against attackers. Leech seed allows you to beat sheddy and recover sub health and stall for more boosts. Stored power owns stuff after a few turns of stalling. Potentially could use taunt or spore instead of magic coat, but I haven't tested that.