Skarmory: 252 Sp Def, 129 HP, 129 Def is a better EV spread. It doesn't need any boost in Attack. Toxic is nice over Rest. Give Leftovers
Ludicolo: 252 HP, 129 Def, 129 Sp Def is a better EV spread. Surf/Ice Beam>>Dive.
Milotic: EVs are better at 252 HP, 129 Def, 129 Sp Def. Surf>Wrap, it needs some power and the trapping contradicts Spikes.
Ampharos: You could switch the Def, and Sp Att EVs. Give Leftovers.
Flygon: EVs 252 Att, 252 Speed, 6 HP. Return>Body Slam. HP Fighting>Screech. Give Leichi Berry.
Entei: EVs: 252 Sp Att, 252 Speed, 6 HP. Timid>Relaxed. Relaxed should never be used on any Pokémon. Flamethrower, Solarbeam, Sunny Day, Calm Mind. Give Salac Berry.
You need a tank. Your EVs are messed up. Since this is for Coloseum, find alternitive items. I despise item restrictions.