PvP Class Guide
Warrior - Brings a good snare and good melee damage. He can charge the casters in the back if he can get in range without entering combat. AoE fear from Intimidating Shout is very powerfull.
Rogue - A great scout. He can sneak up and report the classes so you know what you are up against. Sneaking and opening moves can be risky if the other team has good stealth detection. Still a powerfull melee class even without stealth. Capable of killing any cloth wearer before the cloth wearer is able to react.
Mage - Great CC with polymorph, good single target damage and snares/roots. AoE spells can be very usefull to force enemies to move from an area or take damage. Manashield and Frost Nova gives them a chance to hold up against an attack long enough for other players to help out with CC.
Warlock - Best CC class in PvP. With Seduce, Fear and AoE fear a warlock can break up and control a whole group on his own. Banish is good to counter other warlocks pets. Eye of killrog is the best PvP scouting spell. While shards can be hard to get, healthstones are a big pvp help. Instant cast dots can be thrown on many many people in a short period of time, however a skilled opposing group will quickly nullify them. Damage is a bit low, but CC is very high.
Priest - Great PvP class, I think they are absolutley required. Dispells to destroy enemy buffs and save your side from the enemies dots and cc is very important. Fast heals and shields can help a lot. Also mind flay to stop them from retreating and a powerfull AoE fear to stop them when they rush you.
Druid - In cat form they have stealth and humanoid tracking. They can make excellent scouts because other people cannot track them easily when stealthed and they can track others. Travel form and root is great to catch runners. Root is also usefull for tying up melee type classes. Moonfire is a great instant cast spell that even if dispelled does a fair chunk of damage. Hibernate can be used to CC hunter pets and other druids and shamans in animal forms. Their heals are a bit slow for pvp, but anything is better than nothing.
Hunter - Tracking and Concussion shot are the 2 things I've seen a hunter do that seem the most usefull. With tracking they can prevent the enemy from hiding just out of sight in a building, around a hill or underwater. Concussion shot is a great way to prevent them from fleeing you. Also ranged damage is important in pvp as you are less vulnerable to snares and roots. Your pet can be handy to interrupt casters, but seems more useless than a warlock pet.
Shaman - Shaman seem to have decent melee and spell damage. Earthbind and Fire Nova totems can be deadly if they don't have anyone focusing on your totems. Ghost Wolf and Frost Shock is a great way to catch a runner. Earthshock can be a powerfull spell to stop all sorts of casters including healers. Purge is great to destroy buffs and shield spells.
Paladin - Paladins are very tough to kill, but easy to CC. Because of this I think most paladins will spend their time as a sheep or feared. However they are a powerfull class with good buffs, heals and shields. Cleansing is great to remove CC and dots as well.