My favorite class to run with is probably the warlock. They bring cookies and soulstones, as well as some pretty decent crowd control.
More about what they have to offer, below the break:
“cookies”- Healthstones. These are conjured stones that are like a health potion, but don’t share the potion cooldown. If you’ve ever run with a warlock before, you probably know what I’m talking about. One ‘lock I run with calls it green crack, I prefer cookies (to accompany my mage biscuits, of course).
Soulstones- Extremely useful for those tough fights where AoEs are going off and keeping the tank and dps alive are top priority, and it’s okay to die once. I also like to call this my feign death. Druids have no real way to clear aggro without shifting into cat form, and honestly, I haven’t used my cat cast bar in so long that I don’t even recognize all the spells on it. I’m a strictly /dance cat. Back on track- If for whatever reason I happen to pull aggro (my tank is stunned or otherwise incapacitated, etc.) I have no way to clear threat to make it easier for him to pull and keep aggro. Thus by “feigning” death, I clear aggro and get right back to healing. Of course this is not something to plan on doing and is only for emergencies. It’s more of a feign death with a 30 minute cooldown. As a druid healer, the common “don’t soulstone rez until combat is over” doesn’t apply since you can’t resurrect more than one other person anyway. Take care to die a little bit farther away from the mobs, and then rez in combat so you can throw on a Mad Alchemist’s Potion or Super Rejuvenation Potion and get back to healing so no one else dies. Be smart about it, don’t soulstone rez if the boss is at 60% and the tank and dps are all below 40% health; you almost certainly won’t be able to mana up enough to heal through that fight.
As for their attacks and such, they have great Damage over Time (DoTs) and debuffs. They also have pets, which you should have some level of awareness of.
Imp- Gives a great stamina buff to the party, but doesn’t do a lot of damage, and doesn’t have crowd control
Voidwalker, a.k.a. “Blueberry”- This should probably only be used for soloing, and maybe for off-tanking if really necessary.
Succubus- I once started a dungeon with a level 63 warlock who never bothered to get their succubus. If you ever find yourself in this situation, kick the ‘lock or leave the group and strongly advise the ‘lock to go get their succubus. This is something that is made available to every warlock at level 20. This would be like if a Shaman didn’t bother to get his water totem (something I’ll cover in a later installment of my class overviews). In any case, the Succubus offers crowd control and comic relief (“First we’ll start with a little fire. Am I bugging you, I’m not touching you, am I bugging you, I’m not touching you. There – now you’re hot, and bothered.”). She also has a threat-reduction spell.
Felhunter- This is largely a PvP minion, but it is also useful in some encounters where spell interruption is more useful than crowd control.
Infernal, Doomguard, and Felguard- I cannot think of a reason anyone would want these in a dungeon or raid. If someone else has a reason, please feel free to comment and let me know.
Crowd Control:
Seduce- Cast by succubus; renewable crowd control usable on Humanoids.
Banish- Freezes a Demon or Elemental. The banished being also becomes immune to all damage. Along with the Succubus’ seduce spell, this is most frequently used by Warlocks.
Fear- Be careful with fear, you can gain a lot more mobs than you intend if your feared guy runs into other mobs.
Howl of Terror- Fear x5 for eight seconds
Now you know the ins and outs of what a Warlock has in his arsenal. Feel free to head over to the Warlock WoW Wiki article to get more details on those DoTs and curses. Never assume that the Warlock in your party is a seasoned PvE ‘lock (unless of course they have a full set of T6 gear), and don’t be afraid to ask them to get out a different pet for different situations.

What else the Warlock has – Curses! One is a DoT (Curse of Agony), the others are useful in specific situations.
Curse of Recklessness is the anti-Fear and prevents runners. Curse of Elements – especially now after 2.4.3 – causes the target to be more susceptible to Arcane, Shadow, Fire, and Frost damage. Overall party / raid dps will probably increase with the lock using CoE over CoA, especially with mages, boomkin, & elemental shaman in the mix.
Curse of Tongues slows down casters, while Curse of Weakness reduces the mob’s melee damage.
I’d also mention that the ‘lock has 3 different Fear abilities – regular, Howl of Terror, and Deathcoil. That’s a lot of fearing, lol.