Much of your time in Outland will be spent in heroic dungeons, for both the daily quest and to obtain epic level gear and badges of justice, which are used to purchase powerful items. One of the best classes to take you through these difficult heroics is the Warlock. Aside from its outstanding DPS, Warlock has access to a wide array of tools and utility. These include:
Crowd Control: Warlock is equipped with a few important pieces of crowd control. Succubus is great at holding one enemy away from the fight (though make sure to reapply it when it runs out), though it is fickle at times, and the seduce can often be resisted or broken. Fear is useful in a pinch, and Death Coil can get an enemy off you or a healer long enough for the tank to taunt it off. It should be cautioned that fear should be used sparsely and only in complete emergencies. One wrong fear can send an enemy right towards another pack, pulling them all towards you.
Utility: Soulwell for Healthstones for the party, Soulstones for wipe protection, and a wide variety of demons to select from. The Felhunter can prove useful if interrupts or dispels are needed, the Succubus is always versatile, and the imp can provide a healthy stamina boost.
AOE: Seed of Corruption is a powerful tool to deal with large pacts of enemies – watch your threat, though! Furthermore, if you spec into the destruction tree, using Shadowfury is both good for AOE damage and a 2 seconds stun. There is nothing more exciting than getting 5 or 6 Seed of Corruptions out on different enemies and blowing them all up with a single Shadowfury.
And, when it comes down to the crunch with an intense boss fight, warlock has extremely high DPS to melt through the bosses. When it comes to turning in your hard-earned badges of justice, Icon of the Silver Crescent is a must-buy.