How can I improve my team /vp/?

Speed Deoxys (4 Hp, 252 Atk, 252 Spd): Psychic, Stealth Rock, Spikes, Extreme Speed

Mega Mawile (252 Hp, 252 Atk, 4 Def): Sucker Punch, Iron Head, Swords Dance, Play Rough

Starmie (4 Atk, 252 SpA, 252 Spd): Rapid Spin, Hydro Pump, Ice Beam, Psychic

Latios (252 SpA, 4 SpD, 252 Spd): Draco Meteor, Psyshock, Ice Beam, Hidden Power (Fire)

Milotic (4 Hp, 252 SpA, 252 Spd): Ice Beam, Hidden Power (Grass), Recover, Hydro Pump

Regirock (252 Hp, 252 Def, 4 SpA): Ancient Power, Superpower, Iron Defense, Hyper Beam