Resto Shamans are the bane of an Affliction Lock's existance. Dispel everything, hide tremor totems where they're hard to get to while your partner keeps the Lock snared so he can't get to the tremor totem to knock it down.
Warriors are brutal against us too, due to having every tool in the game to shut us down and stick on us permanently.
I'm not sure what scenario you're talking about here, but if you're talking 1v1 then the only class that truly counters a Warlock would be a Unholy DK. They have all the tools they need to shut down a Warlock even if the Warlock is kiting him perfectly. The fact that the Lock can never stop moving so he can't get any cast times off (or risk the DK closing the distance and just melting face) means the Lock won't be doing much dps, meanwhile the DK will have an enraged pet beating the Lock down and shooting death coils, icy touches, pet stuns, and even a well timed Strangulate to keep the Lock from getting much damage off.
Warlocks are an interesting class in a team scenario. They aren't very dangerous if they have a melee on them, but they aren't exactly squishy which makes them difficult to bring down. The difference between a good Lock and a bad Lock is how well they can perform when being focused.. how good they are at juking, balancing offense and defense, while still being able to land those Fears between interrupts.