1. Unholy Death Knight Overview
The Unholy specialisation currently provides moderate single target damage, as well as excellent cleave damage against 4+ targets. It is better in this regard when compared to many other specialisations.
2. Patch 8.1 Changes for Unholy Death Knights
Festering Doom has been replaced by Magus of the Dead Icon Magus of the Dead.
Helchains has replaced Horrid Experimentation Icon Horrid Experimentation.
A new Azerite trait was added, Cold Hearted Icon Cold Hearted.
The talent All Will Serve Icon All Will Serve now scales properly with Haste.
Death Strike Icon Death Strike's cost was reduced by 10 Runic Power and also received a 20% healing buff.
3. Unholy Death Knight Strengths
Strong single target, AoE, and cleave DPS depending on talent setup
Excellent damage-mitigation capabilities
High raid utility in the form of Death Grip Icon Death Grip and Asphyxiate Icon Asphyxiate
Has ability that provides immunities to knockback and movement-impairing effects
4. Unholy Death Knight Weaknesses
Poor target switching due to Festering Wound application
Lack of damage immunity
Low movement speed
A variable amount of ramp-up time before it can deal effective DPS (due to the application of Festering Wound Icon Festering Wounds)
5. Unholy Death Knight Viability in the Current Patch
Unholy Death Knights are currently outshined in Uldir in comparison to Frost Death Knights. Unholy's current strength is in their burst AoE, which Uldir does not require much of. Unholy is very strong for trash pulls in Mythic+, with the ability to solo very large trash pulls with the right build.