Ninjask: You don't' need to change the item if you use this EV Spread: 252 HP, 4 Defense/Sp. Defense, 252 Speed. This will enable more Leftover healing, but if you don't want you to lose more HP from Sub, then use U-Turn b/c even Battle Frontier leads have Taunt these days and it will screw Ninjask, if you use U-Turn then you can score a hit (if not a weak one) when they set up Taunt and get out of there, too.
Shuckle: Why use Sludge Wave? Seems random to me. Try Toxic or Attract for some stalling. IF you want, you could replace Gyro Ball with Mud Slap to kill accuracy. IF you do, try for a Bold/Impish nature instead to give Power Split more power. (No joke intended)
Alakazam: Good except you won't want Psyche Up as he is a come in and sweep until you go down kind of sweeper. Try replacing Energy Ball and Psyche Up with Shadow Ball and HP Ice for the best coverage. Otherwise good.
Weavile: That... is a weird Weavile. Life Orb is good, but why use Surf with Adamant Nature??? You don't even have Ice STAB! Try Ice Punch/Ice Shard instead of it, and Beat Up only works if WEavile is your lead, otherwise your other Pokemon will be Kod and it won't be effective. Try Night Slash. The standard, great power, and a nice critical hit ratio. Assist is pushing it, don't take any chances. Try Aerial Ace or X-Scissor instead for coverage. Oh, and the EV spread needs to be 252 Attack, 252 Speed, 4 HP. Weavile is not a tank.
Rhyperior: First off, a tank does not need a Focus Sash, as it won't be effective with Rhyperior's massive defense. You could try Leftovers, or White Herb for Superpower. Either way, replace Brick Break with Stone Edge for power and STAB. Shock Wave also needs to go for Megahorn. Change the EVs to 252 Attack, 252 Defense, 4 HP.
Haxorus: Needs to be switched. Not powerful enough. YOur team so far has: 1 wall,(Shuckle) 1 bp passer,(Ninjask) 2 sweepers,(Alakazam & Weavile) 1 tank. (Rhyperior) You need another tank, preferably special. Gardevoir will work.
Gardevoir @ Leftovers
EVs: 252 Sp. Defense, 128 Sp. Attack, 128 HP
Role: Your Special TAnk =D
Moves: Calm Mind (For boosting, a move that all special tanks must have), Will-O-Wisp (Nice burning and makes up for the low Defense that Gardevoir has), Psychic(STAB and your attack), and the last move can be one of the following:
Attacks: Energy Ball, Charge Beam, Focus Blast, Signal BEam, Shadow Ball
Other Moves: Confuse Ray, Destiny Bond, Safeguard, Healing Wish
I do hope this helped!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
=-) =D ;P <;), :)