Please post your build so we can better help you - ie, if you're affliction I'll know you can use iHoT, etc...
If you're affliction, warriors are butter:
1. Now, the first move a warrior will use is charge (battle stance), which makes them open to fear. If they charge you, immediately respond with iHoT; if you get the drop on them, use regular fear. As soon as they are feared, fill them with idots (you can make a macro to make this faster); you should also be running in the opposite direction from where the warrior is going. *note: use amp-coa if you have it, just to take a little extra out from the warrior's hp; make sure you let coa run its coarse.*
2. Now the warrior (if they're decent) will pop an anti-fear trinket (otherwise they wouldn't attack you, but rather go for easier to beat classes), and immediately switch stances to fury. While in fury, they have two moves which cancel fear (berserker rage and recklessness)- although they essentially only have one (the 2nd is great but on an extremely long c/d - you won't run into this in bg - but maybe in arena/world pvp). Berserker rage lasts for a short time (10 seconds), but it's the only way they can really stay close enough to you to hurt you. If the warrior is low on rage, they're screwed - just stay out of range and keep the dots up; drain-tank if you're hit with an immobilize effect.
3. If the warrior has enough rage, they'll use intercept to catch up to you (as an affliction lock you should be easily out of range otherwise). This will temporarily stun you, and give them maybe 1-2 good hits on you. You can respond either with iHoT or Death-coil; if both of these are on c/d (which they shouldn't be at the same time unless you just vsed a rogue) then you can either drain-tank (if the warrior is near-death) or cast fear (regular). If you cast fear, a good warrior will either interrupt your cast, or use intimidating shout. Luckily, your dots should keep the warrior from bandaging, and eating won't refill hp fast enough for a fight. They're basically stuck with giving you 1-2 white hits. When you're mobile, check your cd on iHoT and DC - if the delay is 5-10 seconds, it's smarter to run (random directions) so you can use it (this takes you to step 4); if the cd is too long, just drain-tank them.
4. If the iHoT or DC lands, then you'll have enough time to redot, add in immolate and UA if you have it, and then drain-tank them to death.
I don't know how to beat warriors as either demo or destro spec (not my forte). Good luck playing :)