I hear a lot of comments about this combo, saying that it's hard for Druid/Hunter, and I'm not exactly sure where that stems from. If you know it's a Lock/Druid team put on some PvE gear if you have it, and if you want to cheese it, 120 or so SR. Remember to Arcane Shot both targets to get their buffs off.

Start off by running up to a pillar and dropping a frost trap, you will need it to kite the Warlock and slow his pet. If the Warlock rushes, start DPS on him, and Viper Sting him. Do this until his Druid pops out of stealth, and then throw a Viper and your pet on the Druid. Basically, your goal this fight is to drain the Druid's mana, take as little damage as possible, and kill the Warlock pets. Continue to DPS the Warlock, and when the Druid tries to go off and drink, or you have a good view at his pet (probably felhunter at this point), open up on it. Aimed Shot is incredible for killing pets, and draining mana even more. Have your Druid CC their Druid when he comes to heal the pet. Get out of Line of Sight of the fears the Warlock will definitely try to hit you with. If the pet is still alive, continue to DPS the pet, this essentially drains their mana faster than anything you could do with Viper Sting, and makes the Warlock eat stings. Once the first pet is dead, he will probably Fel Domination a Void Walker; you can anticipate this, have his buffs down, interrupt his casting, and dispel it with Arcane Shot if you timed everything well. I'm assuming that the Warlock will have his pet on your Druid, but if he has it is on you to avoid damage to it, or on your pet to eat HoT's, there is no possible way you can lose, so this is a good situation. If the Warlock gets his pet back up, continue to DPS him while Viper Stinging the Druid, and Silence the fears.

This is not a short fight; you and your Druid will need to drink several times. You must not allow your Druid to get mana drained, and you'll need to open windows in time very often for him to drink. Most of the time Warlocks will spam Drain Mana on the Hunter, which isn't that big of a deal, because you can Feign Death + Drink whenever you want to, and you should have a great deal of mana regen. If the Warlock chooses to bring out a VW with his Fel Domination they no longer have the ability to dispel and you can Freeze the Warlock in order to get him off your Druid. Whenever your Druid needs to drink, Wing Clip the Warlock pet, Warlock, and Druid. Do whatever else you can to stall them, such as Scare Beast and Scatter Shot. If they continue to DPS you when your Druid goes to drink, you'll need to LoS as well as you can to avoid damage until your Druid returns.

Once the pets are dead, start DPSing the Warlock down while not forgetting to drain the Druid's mana, even if he is at 0. Save all of your interrupts for hard recasts and don't waste more than what is necessary. Have your Druid help you, if you don't have an interrupt, have him Cyclone or Feral Charge. If the Warlock fears you, there is a good chance he is going to attempt a hard recast of his pet. Your Druid will need to take care of this.

This combo puts out very low DPS. One game my Druid and I got into a game that started off kind of rough, I was at 30% health, he was at 500 health, 500 mana, and we ended up winning the game through thorough use of LoS and Lifebloom.

Druids Perspective
This match requires the most communication between you and your Hunter more so than any other single DPS/healer combo. You need to talk to each other about his fear DR's and set up to kill the pet, who's going to stop the pet summon, and when you need to set up a drink.

At the beginning you need to make sure to stay out of LOS of the Warlock. If you're in Nagrand/Blade's edge, pillar humping is best, only coming out to Cyclone the Warlock when he drains your Hunter. On Ruins, you need to be in Bear Form because you can't LOS the drains as easily.

With your Hunter beating on the Warlock, the pet will take Soul Link damage, and when it drops to around 60-70%, throw a Lifebloom on and try to go for a pet kill. Drop to bear, and walk into LOS so your Hunter can burst the pet down. The Warlock will fear, so Feral Charge -> Bash him. From there, Rotate Cyclones on the Warlock and Druid so they can't CC the Hunter with Cyclones or Fears. (Cyclone one, immediately start casting on the other, immediately switch back, etc). If the pet dies, CC the Warlock and try to prevent the summon. If he gets it off (he usually will), simply repeat this strategy until it is down again.

This fight, while long, is actually one of our easier ones, they have almost Zero way to actually finish you off. Lifebloom can keep you alive through the Warlocks damage for a long time, so don't give up if you go completely OOM, you can almost always come back.