Basic Information
Unholy is a heavy shadow spell/disease damage spec as well as the best steady aoe damage spec. Full-strength Pestilenced diseases without aoe damage cap are generally awesome in mass aoe.
DPS: Unholy relies a lot more on the pets for dps. Pets get the master's hit rating and attack power but not expertise rating, so getting hit capped is more important than expertise capped. Expertise is useful to stabilize rotations. Strength is the primary stat to gem for. Haste is a good secondary stat which will also increase the rate at which your ghoul attacks. Mastery is okay now since they changed it to shadow damage increase.
Unholy DKs use Unholy Presence.
Tanking: Removed, RIP.
Talent Builds and Rotations
Unholy DPS
Example:
Single Target DPS:
Dark Transformation, Unholy Frenzy, Gargoyle, Sudden Doom - Every time they become available, use them. Unholy Frenzy and Gargoyle have the same cooldown, so try to use them at the same time.
You will open with Outbreak, then alternate between these two sets, throwing in Death Coils as needed and using an unholy rune on Dark Transformation as needed as well as refreshing diseases whenever they fall off:
1. Scourge Strike x 2, Festering Strike x 2
2. Scourge Strike x 6