Improve my Team! (Pokemon B/W)

Hello hello hello! Leah Liang again, your friendly parasol lady at your service~

I got a way cool medal thing on my name which I'm pretty happy about. But that's not what this post is about!

I was wondering if anyone had any constructive criticisms for my Pokemon Black team, which lost three times out of five against my friend in some sorta-notsosorta close matches. (they varied anywhere from 3-6 to 5-6). most of it can probably be stacked up to my inexperience in competitive battling, but I tried to do some research on the current metagame and such so I didn't bring a knife to a gunfight. Anyways, here there are:

Porygon-Z Lv.94 @ Focus Band
EV's: 252 sp. atk / 252 spd / modest
Signal Beam
Nasty Plot
Psywave
Tri-Attack

Ferrothorn Lv. 100 @ Leftovers
Ev's 252 sp. def / 252 HP / Sassy
Protect
Leech Seed
Stealth Rock
Gyro Ball

Togekiss Lv. 97 @ King's Rock
EV's: 252 HP / 252 Def / Calm
Air Slash
Thunder Wave
Aura Sphere
Roost

Jellicent Lv. 100 @ Water Gem
EV's: 252 HP / 252 Sp. Atk / Hardy
Water Spout
Ice Beam
Protect
Shadow Ball

Hydreigon Lv. 99 @ Life Orb
EV's: 252 Sp. Atk / 252 HP / Mild
Dark Pulse
Dragon Pulse
Earth Power
Flamethrower

And the last slot is switched between:

Epseon Lv. 100 @ Focus Sash
EV's: 252 Sp. Atk / 252 Spd / Timid
Shadow Ball
Calm Mind
Baton Pass
Psyshock

and

Haxorus Lv. 99 @ (Whatever item I can give him LOL)
EV's: 252 Atk / 252 Spd / Jolly
Dragon Tail
Dragon Dance
Dragon Claw
Earthquake

===

I get walled pretty easily because Ferrothorn is my only counter to high def/hp pokes, which my friend always tries to whip out AFTER he knocks Ferrothron out...