Ghostcrawler just tweeted that you can now make multiple Death Knights in 5.3.
Patch 5.3 - Hotfixes
Divine Protection should now be usable while stunned.
Thrash periodic damage component can once again be affected by critical chance.
Solar Beam and the Symbiosis version of Solar Beam Silence effect can no longer be reflected.
Elemental Overload version of Lava Burst should now properly deal 75% of the damage dealt by the Lava Burst that activated it.
Fire and Brimstone can now only be cast when the Warlock has at least 1 Burning Ember active.