Greetings. Your usual master, Daniel Whitcomb, is out accumulating bones for his tier 13 set, so I'm filling in. Today, we'll discuss a topic that's received some attention lately in the WoW community and here on WoW Insider: the soloing of old raid and dungeon content. Why go solo? Well, there are many good reasons. Rewards are plentiful: achievements, gold, and transmogrification loot can all be harvested from older dungeons and raids.
If you're not interested in the rewards, though, try it for the challenge. Since the majority of the game's single-player content is tuned to be accessible to all, there are very few options for the solo player looking for something difficult. For harder bosses, you'll have to know your rotation, your cooldowns, and your enemies intimately. For the most difficult bosses, it's quite typical to need a night or nights to perfect your strategy and execution -- when to use cooldowns, what time to move to pick up adds, etc. If this interests you, you're in luck; death knights are generally acknowledged as the class that's best suited for soloing pursuits.
The best soloers
What makes DKs so good at soloing? First, they're a tanking class. This may seem obvious, but most DPS classes (except hunters and locks with pet tanks) are not very well suited for taking consistent punishment. A DPS class can typically only solo bosses that they can DPS down before they die; tanking classes can survive for a while, since their gear and specialization causes them to take much less damage.
Second, they have excellent self-healing. This is balanced for current content by them taking a bit more damage overall, but in a soloing scenario, the incoming damage is vastly reduced, letting them have a chance to compensate. Death Strike is absolutely godly for self-healing compared to a feral's Leader of the Pack, a warrior's Blood Craze, or a paladin's Seal of Insight. More importantly, though, they can get that healing while still keeping up reasonable DPS, unlike a paladin who sacrifices a significant amount of DPS by using healing abilities.
Finally, DKs have the best tool kit in the game to manage various boss abilities. They can do a bit of ranged damage for bosses that fly. They have not one but two AOEs for handling adds. They have two interrupts, as well as on-demand magic immunity. They even have (temporary) pets. Not all of these things are useful for every fight, but as a whole, it means there are very few bosses that a DK can't at least attempt with some success.
When tackling a dungeon solo, there are several things to keep in mind. First, make sure you are specced and geared appropriately. While older bosses hit less hard than bosses in current content, you will still need an appropriate tanking spec to reduce the amount of damage to take to a reasonable level. (Very light-hitting/low-HP bosses, such as those in Karazhan/Molten Core, can be burned down by frost/unholy death knights, but anything else may give you trouble.) Your basic blood tanking spec and glyphs should work fine, though you may want to tweak a few points for specific fights. Notably, there are a few encounters with Mind Controls that only activate if there are multiple targets; for these, you'll have to forsake your Ghoul and Bloodworms.
Gear-wise, things are just a bit different from the normal blood strategy. Obviously, you want the best gear you can get, especially a good weapon, since your DPS is all you have. For gemming and reforging, you want to either focus on stamina or mastery. Extra stamina will increase your HP, which increases the healing of your Death Strikes. Extra mastery will increase the size of your Blood Shields, effectively lowering your damage taken.
The one thing you don't want, however, is to reforge/regem for avoidance stats such as dodge or parry. You want to take a few hits to keep your Vengeance rolling, which will increase your DPS. It can work, but it's not optimal.
The second key factor is maximizing your use of Death Strike. As with regular tanking, you'll want to fire off as many Death Strikes as you can to stay healed up and keep a strong Blood Shield going. This means the usual game of "rune tetris," or depleting your runes as fast as possible so they have a chance to be refreshed by Runic Empowerment procs.
The third key factor is reading up on each boss encounter, so you know which of your abilities you'll need to use when. Some bosses require interrupts or add killing, so you'll need to be prepared with Mind Freeze or Heart Strike/Death and Decay. Other bosses are relatively simple and are simple gear checks. Above all, the two key abilities you'll need to time properly are Anti-Magic Shell and Icebound Fortitude. AMS will let you dodge most of the nasty boss debuffs and has a short cooldown; use it frequently. Icebound Fortitude is more of an emergency cooldown, for the times where your HP dips low and you don't have the runes for a Death Strike.
Tackling the gamut
So what can you kill? Well, you'd be surprised. A reasonably geared DK alt (say, JP/VP gear) can easily handle the majority of the game's level 60 content, level 70 up to tier 6 (most bosses), and level 80 heroics. A heroic-geared DK can push the limits, soloing Kael'thas and Lady Vashj from tier 6 and large parts of level 85 raids.
Several of you may have heard of Mionelol; the preeminent soloing DK, his YouTube videos are quite popular in the WoW community. Having soloed multiple bosses from ICC (including the Lich King), several bosses from current heroics, and at least one Cataclysm raid boss, he is a force to behold. Check out his interview with Manaflask here, and feel free to discuss DK soloing in the comments!
Learn the ropes of endgame play with WoW Insider's DK 101 guide. Make yourself invaluable to your raid group with Mind Freeze and other interrupts, gear up with pre-heroic DPS gear or pre-heroic tank gear, and plot your path to tier 11/valor point DPS gear.