Warlock in PVP?

[Sham]

Here is old screenshot from vanilla of my blue geared SL warlock:
http://i.imgur.com/nY8k1PE.jpg

So I guess they were fine
Fully epic geared SL warlock is pretty much unbeatable in 1v1. You cant kill them quickly since they tank tons of dmg (alot of stamina +30% hp from SL +crazy resists if using felhunter). They put 4 dots on you then just drain life till u die. Without gear warriors particularly will give you troubles. Alot of what Neric wrote is also relevant for vanilla. Its really hard to kill holy priest as a warlock (SP is easy) because they burn your mana fast and some classes can just run away from you in open PvP.

WoTF is not such a big deal as people above say. It obviously gives benefits against you, but deathcoil helps alot. Besides it will be easier to duel as alliance.

[Trance]

Stamina heavy tank locks were the best duelers at Level 60.

There was a warlock named Azael (currently works for Riot Games now) who was infamous for being nearly undefeated in Vanilla WoW because of his skill + his PvP/PvE gear. Watch Ming Videos for reference.