WotLK Classic Unholy Death Knight Stat Priority

1. Hit to cap;
2. Strength;
3. Haste;
4. Armor Penetration;
5. Critical Strike;
6. Expertise;

Hit Rating is crucial as the largest limitation on Unholy Death Knight's damage is Rune cooldowns, so it is important to make sure you are getting the most out of each Rune spent which means ensuring that each attack hits. Hit Cap for 2h Unholy is 8%.

Strength is the best pure DPS stat for Death Knight as it increases Attack Power and Critical Strike. You also rarely have to sacrifice Strength for another stat are you often have to do with secondary stats.

Haste not only increases your personal attack speed but summoned minions such as your Ghoul and Gargoyle gain 100% of the benefit from your Haste rating. Your permanent Ghoul will dynamically update to benefit from your current Haste, but your Summon Gargoyle and Army of the Dead ghouls will snapshot the Haste value you have active when summoning them, so make sure to take advantage of any temporary Haste buffs before summoning them.

Armor Penetration increases the Physical damage you deal to targets up until a cap that will not be realistically obtainable until Icecrown Citadel. A large majority of Unholy's abilities deal Physical damage and benefit greatly from the reduced Armor you will be attacking thanks to the Armor Penetration stat.

Unholy greatly benefits from Critical Strike rating as you have so many small instances of damage going out thanks to effects such as Wandering Plague and Necrosis.