Plate gear as a Death Knight

While you should be looking primarily at plate gear as a Death Knight, be open to mail armour if it has significant stat upgrades from your current plate gear. The goal as a DPS Death Knight is to cause enough 12sky2 Gold to kill your opponent first. While it is nice to be able to take a few hits, if you get a big enough damage output increase it's worth sacrificing some survivability for it. As a Death Knight tank you do not use a shield, so your health, avoidance (Dodge and Parry), and mitigation (damage reduction due to armour value) are all critically important.  Therefore staying in plate armour is really your only choice, so never choose any other armour over plate no matter what the stats. To do this, you need to cause enough damage, and be able to absorb or avoid enough of the incoming attacks while staying alive. The most important stats on gear while tanking are Stamina, Strength, Defense, Expertise, Dodge, Parry, and Armour value.