Powder Horn

Powder Horn
Can You Please Rate My Pokemon Diamond Team?

*All Pokemon on lvl 100*

Tangrowth:
Sludge Bomb
Power Whip
Leaf Storm
Sleep Powder

Staraptor:
Fly
Steel Wing
Close Combat
Brave Bird

Rhyperior:
Thunder
Earthquake
Mega Horn
Rock Wrecker

Infernape:
Flamethrower
Close Combat
Flare Blitz
Rock Climb

Gastrodon:
Recover
Surf
Mud Bomb
Ice Beam

Metagross:
Shadow Ball
Hammer Arm
Meteor Mash
Zen Headbutt

Nice team, it has a good variation of types. Just one small problem, which are the help items. All right ill go one-by-one giving you the best advice as I can.
Tangrowth:
I want to get this guy, I think this one is a special sweeper so I see no point on having power wip, I would recomend replacing it for earthquake. Make it hold a white herb so your sp. attack wont get lowered when using leafstorm. Watch out the white herb will only be used once.

Staraptor:
Perfect! you have just found the perfect moveset for staraptor except for fly, which has bad accuracy and is easy to avoid. Make staraptor learn natural gift, then hold a hondew berry so it becomes a physical ground type attack with 80 base power, so you can kill electric types.

Rhyperior:
Just one adjustment, make it change thunder for thunder fang because he has more attack than special attack and also thunder has a bad accuracy, then make it hold a focus sash or life orb.

Infernape:
BAD! a good moveset for a infernape shoudl be close combat, flare blitz, thunder punch and rock slide, believe me thi is the best for your infernape.

Gastrodon:
AWESOME! only make it hold the leftovers so it recovers some health and it is a great gastrodon.

Metagross:
JUst one adjusment, get rid of shadow ball and isnteadmake it learn earthquake.

Maybe this info wasnt so good as you expectred but HEY I supose it is the best for your team. However try it out at pokemon battle and lets see how it comes out.