Excellent offensive and defensive CDs. Copious AoE burst damage, self-heals, and incredible movement make HDH the preferred choice (IMO) for boosting or speedrunning either timewalking or normal dungeons from any expansion. When geared can solo heroic DF dungeons quite handily as well. Spec into talents that buff Throw Glaive once you get your 4-piece tier set!

Can do some cool dungeon skips with movement skills (a handful of which can be replicated by evokers, but they don't have double jump...)

Double jump, Fel Rush, Glide, Pursuit talent stacks with speed stat.

Super fun in PvP

Go for critical strike and mastery. Once at 35-40% crit, sub for vers or haste. Mastery is kinda OP, don't shy away from it, but still use dual Wafting Devotion.

Great at chunky pulls. A lot slower than havoc in terms of damage, but also a lot, erm, tankier. Even better self-heals. Queue for DF heroic dungeons and grab the whole room. Possible to solo (non-DOTI) mythic 0 dungeons.

Still can get speed from mastery via Pursuit, but mastery itself isn't as good for vengeance as it is for havoc. Still good as a third stat.

Can do all the same skips as havoc. If you need Fel Rush for a worthwhile skip, just switch! Infernal Strike has its own set of skip uses.

Go for haste and versatility till it feels good, then mastery

An old favorite for soloing all kinds of content throughout WoW's history.

More durable alternative to havoc DH, although self healing is more reactive and less passive. 

Capable of huge AoE or ST burst depending on build, although cannot clear dungeons quite as fast as havoc DH. Popular for open world farming.

Prot is less damage (especially in ST), but waaaaayyyyyyyy tankier (obviously).

Ret is incredibly deadly in PvP with multiple burst and utility spells, prot is a royal pain to kill.

Stack haste and vers to about 40% each, then go crit for PvE/mast for pvp.

Super high burst damage even with moderate gear. Great at burning down packs or bosses. Bloodlust for when you really need it. Awesome for carrying queued groups, can solo heroics with careful pulls. A lot more risk/reward than DH.

Relatively high armor, but still feels squishy. Only a couple instant self heals and defensive CDs. Some AoE CC and casting while moving via hover.

No double jump, but Glide and Hover still allows the use of certain skips. Faster bunny hopping than other dracthyr.

Go for haste and critical strike to 35-40%, then choose either mastery or versatility. 

Most excellent in PvP, does a bit of everything with fantastic mobility. 

Kind of a weird choice in solo PVE, but still effective, and will hard carry groups. Do your job of making the tank feel badass. CAN solo heroics when geared, if you really want to, but pull sensibly. Fantastic and a bit OP in PvP.

Shadow melts through bosses and medium-size packs with ease during Voidform and Void Torrent. Spec into Idol of Yogg Saron once you get your 4-piece tier set!

Shadow in general is less tanky than disc- be mindful of this. Use CC. Disc does notably less damage but heals a lot more, with absorbs galore (obviously). 

Sometimes you definitely want more damage, sometimes more healing. Choose depending on the situation.

Shadow: 35-40% haste, 17-21% mast, then crit.

Disc: 30-40% vers, 30% crit, then mast or haste depending on preference.

Haste/vers for both in PvP